How Accurate Are DeepL Translations? Comparison with Google Translate, ChatGPT, and Microsoft Translator for Business Emails!

1. Four Translation Tools

The following sections offer brief introductions to the features of each tool that we compared.

1-1. DeepL Translation

DeepL is a neural machine translation service based in Germany. It is highly regarded for its deep understanding of context, producing very natural and fluent translations. It is especially well-known for accurately reproducing complex sentences and polite expressions.

・Strengths: Natural and highly accurate translations, contextual understanding, ability to switch between plain and polite forms (paid version)
・Weaknesses: Slightly fewer supported languages compared to other tools (though the major languages are covered)

1-2. Google Translate

This is the most famous and widely used machine translation service. It boasts an overwhelming number of supported languages and translates extremely quicly. Its multifunctionality is also worth noting, including full webpage translation and voice translation.

・Strengths: Overwhelming number of supported languages, translation speed, multifunctional mobile app
・Weaknesses: It occasionally produces unnaturally literal translations and requires extra care with formal business expressions. Because it is a free service, there are also issues regarding confidentiality.

1-3. ChatGPT

ChatGPT is a conversational AI system developed by OpenAI. Its greatest feature is its flexibly to reflect a range of instructions, such as "make the text more polite" or "emphasize this nuance," not just simply translate. It is can also generate multiple translation variants to choose from.

・Strengths: Customizability of expressions, flexible responses according to context, and capability to perform tasks beyond translation (such as summarizing and proofreading)
・Weaknesses: Because the system is not dedicated solely to translation, responses can be somewhat slow, and crafting prompts (instructions) is necessary.

1-4. Microsoft Translator

This is the translation service provided by Microsoft. A major benefit to using it is the strong integration with Office products such as Word, Excel, and PowerPoint, as well as Teams, facilitating the seamless translation of business documents.

・Strengths: Strong integration with Microsoft products and convenient for translating business documents
・Weaknesses: Literal translations that often sound unnatural

2. [Practice] Thorough Comparison of Translation Accuracy in Business Emails

We compared the Japanese to English translation results of each tool using specific example sentences that resemble the content of business emails,.
In Japanese business emails, there is a culture of using long, prefatory phrases, aka "cushion words," such as "お忙しいところ恐縮ですが (I apologize for bothering you when you are busy)" and "お手数をおかけしますが (sorry for the inconvenience)," to express maximum consideration for the recipient.
On the other hand, English business emails tend toward more direct and concise expressions, while maintaining politeness. Showing too much humility can be perceived as redundant and confusing. So, let’s see if and how each translation tool handled this cultural difference.

2-1. Example 1: Polite request email

The following table shows the Japanese example sentence used and the translation results generated by each service.

Japanese	お忙しいところ恐縮ですが、添付の資料をご確認いただき、明日正午までにご意見をいただけますでしょうか。
DeepL	Thank you for your time, but please review the attached documents and provide us with your feedback by noon tomorrow.
Google	I apologize for bothering you during your busy schedule, but could you please review the attached documents and provide us with your feedback by tomorrow at noon?
ChatGPT	We apologize for the inconvenience during your busy schedule, but could you please review the attached materials and provide your feedback by noon tomorrow?
Microsoft	We apologize for your busy schedule, but please check the attached materials and give us your opinion by noon tomorrow.

DeepL's translation converts the original phrase "恐縮ですが" into a positive expression commonly used in English business contexts, “Thank you for your time.”
This localization approach is a successful "translation" of Japan's culture of modesty into the English-speaking culture of gratitude. The request part, “please review…,” is direct but natural in a culture that prefers conciseness. Many would consider this an excellent translation with very high practicality.

Google's translation faithfully reproduces the nuance of the original phrase "恐縮ですが" as “I apologize for bothering you.”
It is a very polite and safe translation without mistakes. However, depending on the recipient and the situation, it might be perceived as overly apologetic. Nevertheless, it is the best choice for someone who wants to convey Japanese politeness as is.

ChatGPT's translation, like Google Translate, faithfully conveys the politeness of the original text. The word “inconvenience” has a formal tone that is particularly suitable for emails sent on behalf of an organization.
This translation is another polite and safe choice, but considering English-speakers' general preference for brevity, the preamble might feel a bit verbose. When the recipient requires a high level of formality, this is a good choice.

Microsoft's translation of the opening phrase, “We apologize for your busy schedule,” is a mistranslation that is likely to confuse the recipient.
The thoughtful nuance of the original phrase–more along the lines of, "Sorry to bother you when you are busy"–is completely lost, and the recipient is left with a strange impression.
Also, the choice of words like “check” and “opinion” is somewhat casual and less suitable for a professional context. This level of translation definitely requires correction for business use.

Ultimately, the choice of which tool to use depends on who you are communicating with and what you want to convey.
If you need to interact quickly with startups in English-speaking regions, DeepL's conciseness stands out, while if you are dealing with traditional large corporations or public institutions, the politeness of Google or ChatGPT may provide reassurance.

2-2. Example 2: Situation report and apology email

The following table shows the Japanese example sentence used and the translation results generated by each service.

Japanese	システムトラブルにより、ご報告が遅れましたことを深くお詫び申し上げます。現在、復旧作業を進めておりますが、完了までには今しばらくお時間をいただく見込みです。
DeepL	We deeply apologize for the delay in reporting this information due to system trouble. We are currently working on restoring the system, but it is expected to take some time to complete.
Google	We deeply apologize for the delay in reporting this due to a system problem. We are currently working on restoring the system, but it will take some time to complete.
ChatGPT	We deeply apologize for the delay in our report due to a system trouble. We are currently working on restoration, but it is expected to take some more time to complete.
Microsoft	We sincerely apologize for the delay in reporting due to system trouble. We are currently working on restoration, but it is expected to take some time to complete.

DeepL's translation is overall very natural and high quality. It specifically translates “深くお詫び” as “deeply apologize” and “復旧作業” as “working on restoring the system,” making it easy to understand. However, the phrase “今しばらく” is interpreted as “some time,” which slightly weakens the intended nuance of “a little longer,” but this is just a minor drawback.

Google's translation is very similar to DeepL's but has some differences. The phrase “a system problem” for “システムトラブル” is a more common and natural expression. On the other hand, the text ends with “it will take some time,” which sounds more definitive than the phrase used by other tools (“is expected to"). If you want to convey the same tone of uncertainty as the source text, a slight revision might be needed.

ChatGPT's translation most accurately captures the nuance of the original text. Most notably, it translates "今しばらくお時間をいただく" as “it is expected to take some more time.” By including “more,” it conveys the nuance that the process will take longer than initially expected. This makes it the most reliable translation for capturing even the fine details.

Microsoft's translation interprets “深く” as “sincerely,” which is a very polite expression of apology similar to “deeply” and an excellent choice for business emails. The overall structure is also accurate, resulting in a high-quality translation. However, it is worth noting that the object of restoration (the system) is not explicitly stated and the nuance attributed to “今しばらく” is somewhat weak compared to other tools, leaving slight room for improvement.

For this example sentence, all tools produced comparable results that are hard to rank. ChatGPT stood out a bit by uniquely and accurately translating the delicate nuance of "今しばらく" as “some more time,” which reflects the advancement of AI's contextual understanding ability. That said, all four translations are fundamentally excellent. At this level, just minor adjustments or even using the translation as is should not cause any issues in business communication.

3. [Practical Application] From Preface to Closing: Evaluating "Contextual Understanding" in Full Email Translation

Until now, we have compared the translation accuracy of each tool using individual sentences, but actual emails consist of a series of elements including subject lines, greetings, the main content, and closings. In particular, fixed expressions unique to Japanese business emails, such as "いつもお世話になっております,"a common introduction, and "引き続きよろしくお願いいたします," a common sign-off, have no direct English equivalents.

When measuring the overall capabilities of translation tools, each tool's ability to read the context of an entire email and transform its "set cultural phrases" into natural English is extremely important. Here, in a test of the tools' true abilities, we directed each system to translate a typical Japanese business email in its entirety.

The following table shows the Japanese example sentence used and the translation results generated by each service.

Japanese	Subject: 先日のデモンストレーションのお礼 Body: いつもお世話になっております。 先日はご多忙の折、弊社新製品「＜製品名＞」のデモンストレーションにご参加いただき、誠にありがとうございました。 当日使用いたしました資料を添付にてお送りいたしますので、ご検討の際にお役立ていただけますと幸いです。 何かご不明な点やご質問などがございましたら、いつでもお気軽にご連絡ください。 今後とも、何卒よろしくお願い申し上げます。
DeepL	Subject: Thank you for attending our demonstration Body: We hope this message finds you well. We would like to express our sincere gratitude for taking the time to attend the demonstration of our new product, “Product Name,” despite your busy schedule. We have attached the materials used during the demonstration for your reference. If you have any questions or concerns, please do not hesitate to contact us. We look forward to continuing to work with you in the future.
Google	Subject: Thank you for the demonstration the other day Body: Thank you for your continued support. Thank you very much for taking the time out of your busy schedule to attend our demonstration of our new product “Product Name” the other day. We have attached the materials used on the day, so we hope they will be useful when you consider purchasing. If you have any questions or concerns, please feel free to contact us at any time. We look forward to your continued support.
ChatGPT	Subject: Thank You for Attending Our Recent Demonstration Body: Dear [Recipient’s Name], Thank you very much for taking the time out of your busy schedule to attend the demonstration of our new product, “<Product Name>,” the other day. Please find attached the materials we used during the presentation. We hope they will be helpful for your further consideration. If you have any questions or need any additional information, please do not hesitate to contact us at any time. We sincerely appreciate your continued support and look forward to working with you in the future. Best regards, [Your Name]
Microsoft	Subject: Thank You for the Recent Demonstration Body: Dear [Recipient’s Name], I hope this message finds you well. Thank you very much for taking the time to participate in the demonstration of our new product “<Product Name>” despite your busy schedule the other day. I have attached the materials we used on that day for your review, and I hope they will be helpful to you. If you have any questions or need further clarification, please do not hesitate to reach out at any time. We appreciate your continued support and look forward to working with you.

DeepL's translation is overall very natural and uses polite business English. It is particularly skilled at converting Japanese set phrases into the most appropriate forms for English business emails.
For example, instead of directly translating “いつもお世話になっております,” it replaces this introductory line with the natural phrase “We hope this message finds you well.” Also, it excellently converts the formal closer, “今後とも、何卒よろしくお願い申し上げます” into the future-oriented and positive closing phrase “We look forward to continuing to work with you in the future.” The translation conveys all the nuance of the original text accurately and succinctly, resulting in a polished email of high quality that can be used as is in professional settings.

Google's translation generally conveys the original Japanese intent, but overall, it is fairly literal and contains slightly unnatural expressions.
In particular, the subject line “Thank you for the demonstration the other day” could be misinterpreted as thanks to them for showing us a demo, when they were in fact the audience. Also, the phrase “ご検討の際にお役立ていただけますと幸いです” is translated as “we hope they will be useful when you consider purchasing,” and the direct mention of “purchasing” may put unwelcome pressure on the recipient. Compared to other services, this result lacks the refinement needed in a business email.

ChatGPT’s translation perfectly captures the format of business emails and is characterized by high practicality through the automatic inclusion of placeholders like “[Recipient’s Name]” and “[Your Name]” in the salutation and signature, respectively. Not only does it accurately translate the original intent, but it also adds thoughtful expressions, giving a more polite and considerate impression.
For example, it added the phrase “or need any additional information” for the translation of “ご不明な点やご質問など,” which technically only refers to having questions or uncertainty. It also represented “ご検討” as “your further consideration,” showing more awareness of the recipient's perspective. Overall, it is the most complete translation and offers excellent suggestions.

Microsoft's translation, like ChatGPT's, is presented in a practical format through the addition of placeholders. The expressions are also polite, and the choice of vocabulary is appropriate, like in the translation “to participate in the demonstration” for the Japanese phrase "デモンストレーションにご参加いただき."
However, some parts require slight adjustments to match the context. For example, similar to Google’s translation, the subject line “Thank You for the Recent Demonstration” lacks the word “attending,” making the meaning somewhat ambiguous. Also, the subject of the sentence regarding attached materials is “I" instead of “We,” which may require correction if the sender is writing on behalf of the company. Overall, the level of completeness gives the impression of being slightly behind the other excellent services.

With the translation of an entire email, beyond the accuracy of individual words and sentences, comprehensive "contextual understanding" and the "ability to adapt business customs" are required, leading to larger variation in the capabilities of each tool.
In particular, ChatGPT's ability to offer suggestions that account for the recipient's culture and business context can be said to add significant value that links directly to higher work efficiency.

4. [Applied Use of ChatGPT] Generating English Emails from Bullet Points

So far, our comparisons have focused on each system's ability to translate complete Japanese sentences. However, ChatGPT has not only translation capabilities, but also features for "generating" text. Its ability to create business emails by extrapolating on content from a bulletted list is a unique feature not found in other translation tools.

By utilizing this feature, you can quicly create a natural-sounding draft of a foreign-language email, simply by noting the key points that you want to convey. Since it eliminates the time needed to think about phrasing the source text, this generative feature is expected to improve the efficiency of email creation. Check out the example below, where we generated a scheduling email from bullet points.

4-1. Example: Generating a scheduling email from bullet points

ChatGPT was given the following bullet points and instructions.

Instructions for ChatGPT (prompt)

Please create an English business email based on the following bullet points. ・Subject: 次回ミーティングの日程調整 ・Content: – プロジェクトAの進捗について話したい – 以下の日程で都合の良い時間は？ – 6月10日（月）午前 – 6月11日（火）13:00-15:00 – 6月12日（水）午後 – もし都合が悪ければ、いくつか候補を教えてほしい

ChatGPT's generated result

Subject: Scheduling the Next Meeting Body: Dear [Recipient’s Name], I hope this message finds you well. I would like to schedule our next meeting to discuss the progress of Project A. Could you please let me know your availability for one of the following time slots? ・Monday, June 10 (morning) ・Tuesday, June 11 (1:00 PM – 3:00 PM) ・Wednesday, June 12 (afternoon) If none of these times are convenient for you, please feel free to suggest a few alternative dates and times that would work better for you. Thank you in advance, and I look forward to your reply. Best regards, [Your Name]

Looking at these generated results, we can see features that differ from simple "translation." Most important are the following:

・Intent-aware phrasing: From the fragment of information "プロジェクトAの進捗について話したい," it generated a clear and natural sentence in the realm of business: “I would like to schedule our next meeting to discuss the progress of Project A.”

・Automatic Format Generation: It properly arranged the standard format necessary for business emails, including the subject, salutation, greeting, main content, closing remarks, and signature.

・Automatic Selection of Polite Expressions: When asking about schedules, the system chose the polite phrasing of “Could you please let me know…,” and when requesting alternatives, the expression “please feel free to suggest…” was selected in consideration for the recipient.

In this way, ChatGPT showed its ability to draft English emails based on Japanese notes, taking into account the verbal context and circumstantial background, then using structures and expressions suited to the purpose. This function is closer to a "language composition assistant," rather than a "translator." Many would consider this a convenient tool that shortens the time required to compose emails, thereby allowing you to focus on your core work.

5. Using the Office Add-In "MTrans for Office" to Streamline the Use of Translation Tools

So far, we have compared the strengths and weaknesses of various translation tools, but many of you may be wondering which tool you should ultimately use or lamenting the idea that it's troublesome to switch between applications for every use. While DeepL's natural phrasing and ChatGPT's suggestion capabilities are hard to give up, repeatedly opening a browser to copy and paste each block of translation text is inefficient.

In response to that, we recommend is the add-in tool "MTrans for Office," which allows you to directly call up all the major translation engines that were compared in this article within your familiar Word or Outlook applications.

For example, when composing a foreign-language email in Outlook, you can simply select the text written in your native tongue and press a button to instantly display multiple translation results from DeepL, ChatGPT, and others. Just like in the examples above, you can compare the nuance of the different translations and apply the most appropriate expression to the body text with a single click.

Additionally, MTrans for Office also lets you utilize generative AI via ChatGPT from OpenAI. You can list out the main points of your email, select that text, and click the execute button to automatically generate a translated email based on the summary. By clicking the "Replace" button, you can apply the generated text to the email body. Then, simply by edit the details, like the customer’s name, to complete your email.

MTrans for Office is a tool that allows you to efficiently leverage the strengths of each translation engine introduced in this article directly within your Office applications. Because you can compare and review multiple translation results on a single screen, it helps reduce the work of translation tasks and improves the quality of your communication.

6. Summary

This article compared DeepL, Google Translate, ChatGPT, and Microsoft Translator in the context of business emails, examining the strengths and weaknesses of each. As a result, we determined that DeepL excels at natural translations that capture cultural nuance, while ChatGPT stands out for its ability as an "assistant" capable of generating foreign language emails from bullet points. Each tool has distinct characteristics. Rather than trying to force a single tool to perform perfectly in every scenario, wisely switching between these tools according to the recipient and the purpose of your emails is the key to high-quality communication.

The Office add-in "MTrans for Office" introduced in this article is a tool that seamlessly enables "smart switching" between translation systems within your usual Word and Outlook applications. By using this tool, you can easily compare multiple translation engines and immediately select the most appropriate results. MTrans for Office offers a 14-day free trial. Please give it a try.

Features of MTrans for Office

1. ① Unlimited number of file translations and glossary integration for a fixed fee
2. ② One-click translation from Office products!
3. ③ Secure API connection
   ・For customers who want further security enhancement, we also offer SSO, IP restrictions, and so on.
4. ④ Japanese-language support by a Japanese company
   ・Response to security check sheets
   ・Payment by bank transfer available

 

MTrans for Office is an easy-to-use translation software for Office.