AI Translation from English to European Spanish Translation

How good is AI translation from English to Spanish?

Two or more one-step solutions meet every Basic and Standard requirement in European Spanish.
Only the solution on OpenAI GPT-5.6 Terra with the gender-neutrality agent meets every Advanced requirement in European Spanish.
The cheapest solution that meets every Standard requirement costs $3.74 per million characters, and the fastest takes 17 seconds per 1,000 words.

A solution is a model plus its harness: prompts, glossaries and other context, pre- and post-processing. It meets a quality level when it meets every requirement of the level.

Requirement	Description	Met when
Basic requirements for any company
General translation quality	Translation errors of every type, such as mistranslations, omissions and grammar errors, classified by type and severity following MQM, the industry standard.	No critical error, at most 3 major errors in the four test texts (3,034 words) and at most 20 errors per 1,000 words, weighted by severity (minor 1, major 5, critical 10).
Standard requirements adds the rules companies set for their content
Terminology	The approved translation of every glossary term, in any of its correct forms.	100% of the glossary terms.
Tone of voice	The formal register (usted) in every sentence in the second person or the imperative.	100% of those sentences.
Tags	Every HTML tag of the source, with its attributes, in the translation.	100% of the tags.
Unicode character integrity	Every character intact, with no corrupted characters and no letter from another script that only looks like the right one.	100% of the characters.
Locale conventions	The punctuation marks of the target language in place of the English ones, such as the Spanish ¿ and ¡.	No pass-or-fail bar. We report it as a share, because whether to localize punctuation is a matter of house style.
HTML entities	No HTML character code, such as the code for a quotation mark, that the source does not carry.	No added HTML entity.
Valid JSON	The translated JSON document still parses.	The document parses.
Spacing at tag boundaries	The spaces next to HTML tags stay as in the source.	100% of the tag boundaries.
Advanced requirements adds a requirement for some companies and use cases
Gender neutrality	A gender-neutral translation wherever the English source leaves the gender of a person open, as in “your manager” or “the expert”.	100% of the sentences that refer to a person.

Find English to Spanish translation solutions for your requirements

Pick a quality level, or your own requirements, bars and constraints, to see the shortlisted solutions that meet them in European Spanish, with a column for each requirement you select. Under Optimize for, choose which of them comes first: the one with the fewest total errors, the lowest cost or the shortest time. Click a column heading to sort by it.

The shortlisted solutions on 11 models, with their Intento LQA results. Total errors per 1,000 words add the weighted general translation quality errors (minor 1, major 5, critical 10) to the missed glossary terms, sentences in the wrong register, tag errors and sentences that fail gender neutrality, each counted once. Formatting counts as met or missed and does not add to the total errors. The models that did not make the shortlist have automatic scores only: the shortlist. Gender neutrality: the Advanced requirements count the two best solutions of the language, with the gender-neutrality agent where they need it. The results of the other solutions are shown for information.

How we measure it: 11-01 · 11-02

Trade-offs in English to Spanish translation

Price vs quality

Two one-step solutions meet every Standard requirement in European Spanish at almost the same cost, $3.74 per million characters for OpenAI GPT-5.6 Terra and $3.87 for Google Gemini 3.1 Pro Preview. Translations from OpenAI GPT-5.6 Terra take 17 seconds per 1,000 words against 73 and have 20.1 total errors per 1,000 words against 24.6, so Optimize for selects OpenAI GPT-5.6 Terra for quality, cost and latency alike.

Constraints

Constraints narrow this quickly. Under the Standard requirements, a cost cap below $3.74 per million characters or a time limit below 17 seconds per 1,000 words removes both solutions, and the three real-time solutions on the shortlist, Microsoft Translator, Amazon Translate and DeepL Next Gen, all miss general translation quality and tag handling.

Agent effect

For the Advanced requirements, the gender-neutrality agent on OpenAI GPT-5.6 Terra raises the cost from $3.74 to $3.92 per million characters and the time from 17 to 24 seconds per 1,000 words, and its total errors fall from 20.1 to 6.3 per 1,000 words.

English to Spanish translation quality levels

European Spanish is in tier 1 (simple solution + backup) for the Standard requirements and in tier 3 (one solution) for the Advanced requirements, because only one solution meets gender neutrality.
A solution meets general translation quality with no critical error, at most three major errors and at most 20 weighted errors per 1,000 words.

Optimize for

Basic requirements★★★