What Is the Translation Accuracy of OpenAI's New Model GPT-4.1? A Comparison with DeepL!

1. What is GPT-4.1?

GPT-4.1 is a new AI model released by OpenAI on April 14, 2025. There are three types: GPT-4.1, GPT-4.1 Mini, and GPT-4.1 Nano. The performance increases in the order of Standard, Mini, and Nano, while the cost per token also rises, allowing users to choose based on their needs and budget. These models are available only via API and are intended to be integrated into applications and services. GPT-4.1 has significantly improved its ability to write programs, generate code, and fix bugs more accurately, as well as enhanced translation accuracy. Additionally, the context window has been expanded to a maximum of 1 million tokens, enabling the processing of large texts and documents.

2. Translation Accuracy of GPT-4.1

We will verify the translation accuracy of English-Japanese and Japanese-English translations using our blog articles.

Japanese to English Translation

Source	An abundance of pronouns Stylistically, English has an aversion to repetitious words and phrasing. Subsequently, it has a heavy reliance on the use of pronouns, rather than using the same nouns or names over and over. Linguistically, this is not an issue and is usually easy for an English-speaking audience to understand, but when the English text is simply the starting point for multi-lingual translations, an overabundance of pronouns can cause some problems. As with the positioning of phrases in an English sentence structure, pronouns usually describe the closest relevant antecedent. Therefore, if other relevant nouns appear between the pronoun and the noun that it is meant to describe or if many pronouns are used in long succession, the likelihood of misunderstanding goes up.
GPT-4.1	代名詞の多用 英語は文体的に、同じ単語や表現の繰り返しを避ける傾向があります。そのため、同じ名詞や名前を何度も使う代わりに、代名詞を多用します。英語話者にとっては問題なく理解できますが、英語文が多言語翻訳の出発点となる場合、代名詞の多用は問題を引き起こすことがあります。 英語の文構造における句の位置と同様、代名詞は通常、直前の関連する名詞を指します。しかし、代名詞とその指す名詞の間に他の名詞が挟まったり、代名詞が連続して使われたりすると、誤解の可能性が高まります。
GPT-4.1 Mini	代名詞の多用 英語は繰り返しを避ける傾向が強く、そのため代名詞の使用が多いです。これは英語話者には問題ありませんが、多言語翻訳の出発点としての英語テキストでは問題を引き起こすことがあります。 代名詞は通常、最も近い先行詞を指しますが、間に他の名詞が入ったり、連続して多用されたりすると誤解の可能性が高まります。
GPT-4.1 Nano	過剰な代名詞の使用 英語は、繰り返しの言葉やフレーズを避ける傾向があります。そのため、同じ名詞や名前を何度も使うのではなく、代名詞に頼ることが多いです。言語学的にはこれは問題ではなく、英語を話す読者には理解しやすいですが、多言語翻訳の出発点として英語のテキストだけを考えると、代名詞の過剰な使用は問題を引き起こすことがあります。 英語の文の構造と同様に、代名詞は通常、最も近い先行詞を指します。したがって、代名詞とそれが指す名詞の間に他の名詞が現れたり、多くの代名詞が連続して使われたりすると、誤解の可能性が高まります。
DeepL	代名詞の多用 英語は文体上、同じ単語や表現の繰り返しを嫌います。 そのため、同じ名詞や固有名詞を繰り返し使用するのではなく、代名詞の使用に大きく依存しています。言語学上は問題ではなく、通常、英語話者にとっては理解しやすいのですが、英語のテキストが単に多言語翻訳の出発点である場合、過剰な代名詞は問題を引き起こす可能性があります。 英語の文章構造におけるフレーズの位置づけと同様に、代名詞は通常、最も近い関連する先行詞を指します。そのため、代名詞とそれが指し示す名詞の間に他の関連する名詞が挿入されたり、代名詞が連続して多数使用されたりすると、誤解が生じる可能性が高くなります。

 

Looking at the above translation examples, the translations by GPT-4.1 excel in both accuracy and fluency.

Regarding the areas highlighted in green, while none of the models contain mistranslations, the translation by GPT-4.1, which states "uses a lot of pronouns," is the most natural.

The sections highlighted in yellow are accurately conveying the meaning of the original text only by GPT-4.1. GPT-4.1 Mini has omissions in translation, GPT-4.1 Nano has mistranslations, and DeepL translates the grammatical term phrases as "phrases," which reduces accuracy.

Japanese to English Translation

Source	多言語間でのスムーズな翻訳が可能です。従来の機械翻訳と異なり、AIは文脈や専門分野を考慮した自然な翻訳を提供します。ビジネス文書、技術マニュアル、マーケティング資料など、業界特有の用語や表現も適切に翻訳できます。また、単純な言語変換だけでなく、翻訳先の文化的背景を考慮した表現の調整も行い、国際的なコミュニケーションの障壁を低減します。さらに、翻訳結果のトーンや専門性レベルも調整可能で、対象読者に最適化された翻訳文書を作成できます。
GPT-4.1	Seamless translation between multiple languages is possible. Unlike conventional machine translation, AI provides natural translations that take context and specialized fields into account. It can accurately translate industry-specific terms and expressions found in business documents, technical manuals, marketing materials, and more. In addition to simple language conversion, it also adjusts expressions to reflect the cultural background of the target language, reducing barriers to international communication. Furthermore, the tone and level of expertise in the translated text can be adjusted, enabling the creation of documents optimized for the target audience.
GPT-4.1 Mini	Smooth translation between multiple languages is possible. Unlike traditional machine translation, AI provides natural translations that take context and specialized fields into account. Industry-specific terms and expressions can be appropriately translated for business documents, technical manuals, marketing materials, and more. Additionally, not only simple language conversion but also adjustments to expressions considering the cultural background of the target language are made, reducing barriers to international communication. Furthermore, the tone and level of expertise in the translation results can be adjusted to create translated documents optimized for the intended audience.
GPT-4.1 Nano	It is possible to perform smooth translation between multiple languages. Unlike conventional machine translation, AI provides natural translations that take into account context and specialized fields. It can accurately translate industry-specific terminology and expressions found in business documents, technical manuals, marketing materials, and more. Additionally, it not only performs simple language conversion but also adjusts expressions considering the cultural background of the target language, thereby reducing barriers to international communication. Furthermore, the tone and level of professionalism of the translation results can also be adjusted, enabling the creation of translated documents optimized for the target audience.
DeepL	Smooth translation between multiple languages is possible. Unlike traditional machine translation, AI provides natural translations that take into account context and specialized fields. Industry-specific terminology and expressions, such as business documents, technical manuals, and marketing materials, can be translated appropriately. In addition to simple language conversion, AI also reduces barriers to international communication by adjusting expressions to take into account the cultural background of the target country. Furthermore, the tone and level of expertise of the resulting translation can be adjusted to create a translated document that is optimized for the target audience.

In Japanese-English translation, it is necessary to infer the ambiguity unique to the Japanese language from the context. However, in GPT-4.1's standard and Nano versions, expressions not found in the original text, such as 'found in business documents,' are appropriately supplemented in the highlighted green areas. DeepL is also said to have a high ability to understand context, but in this example, it resulted in a literal translation and could not accurately convey the intent of the original text.

3. Sentence Translation vs Paragraph Translation

The accuracy of machine translation differs between sentence translation, which translates one sentence at a time, and paragraph translation, which translates multiple sentences at once. Sentence translation processes each sentence independently, making it difficult to consider context, which can lead to mistranslations and unnatural expressions. On the other hand, paragraph translation processes multiple sentences together, allowing for a better understanding of context and the ability to provide more natural translations. Therefore, especially in cases with complex sentences or many technical terms, paragraph translation tends to improve accuracy. In particular, the standard version of GPT-4.1 has a high level of contextual understanding, and when faced with ambiguous original text or cases where a literal translation does not convey the meaning, it tends to add wording to the translation, resulting in a more comprehensible output.

4. How to use GPT-4.1 from Office applications

Our MTrans for Office is an AI translation and writing add-in for Word, Excel, PowerPoint, and Outlook. It can translate in conjunction with each application and GPT-4.1. In addition to GPT-4.1, it also integrates with translation service APIs from DeepL, Google, and Microsoft, allowing for easy comparison of translations from each provider. By translating at the paragraph level, it maximizes the contextual understanding of GPT-4.1. It supports file translation, glossaries, and automatic post-editing (automatic correction of translations), significantly improving both the efficiency and quality of translation tasks.

 

5. Summary

GPT-4.1 has a high level of contextual understanding, especially in paragraph translation, providing natural and accurate translations even when dealing with complex sentences and technical terms. By utilizing MTrans for Office, it is possible to integrate multiple translation services, including GPT-4.1, to improve the efficiency and quality of translation work. In particular, paragraph-level translations that leverage GPT-4.1's contextual understanding reduce mistranslations and unnatural expressions compared to sentence-level translations, resulting in more natural translated texts.

Our company offers an automatic translation product, MTrans for Office, with GPT-4.1 model integration. By using the API, you can utilize the translation function of GPT-4.1 without the risk of information leaks. With MTrans for Office, you can call GPT-4.1 from Word, Excel, PowerPoint, and Outlook with just one click, to translate, proofread, or transcribe English emails. You can also create your own prompts. Try the quality and usability of MTrans for yourself with our 14-day free trial offer.

Features of MTrans for Office

1. ① No limit on the number of files that can be translated or on the glossary, with a flat-rate system
2. ② Translate with one click from Office products!
3. 3. API connection ensures security
   - For customers who want further enhancement, we also offer SSO, IP restrictions, and more.
4. ④ Support in Japanese by Japanese companies
   ・Support for security check sheets is also available
   ・Payment via bank transfer is available

 

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