English to Japanese AI translation quality, cost and speed

Find English to Japanese 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 Japanese, 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 13 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. Inconclusive: the three LQA judges agree on fewer than 90% of the sentences of the solution, so it has no general translation quality result (09-02). 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

English to Japanese translation quality levels

• 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 selects one of the solutions that meet the level: the one with the fewest total errors, the lowest cost or the shortest time. Where no solution meets the level, the card shows the available solution with the fewest total errors and what it misses. Total errors count every requirement with countable errors.

One solution per level: the simplest that meets the level, the cheapest of them where several are equally simple. ★ a one-step solution, ☆ a solution with more steps or the gender-neutrality agent.

How we measure it: 11-01 · 11-02 · 08-09

English to Japanese translation requirements

• Of the 11 shortlisted one-step solutions with a conclusive Intento LQA result, 10 meet tone of voice, 8 formatting, 6 terminology and 2 tag handling.
• None of them meet general translation quality.
• With one-step solutions alone, Japanese is in tier 4 (no solution) for the Standard requirements, with two-step solutions (translation + post-edit) in tier 4 (no solution), and with three-step solutions (translation + LQA + repair) in tier 2 (two or more solutions, none simple).

The requirements with countable errors. Every solution with its result on each requirement: the explorer.

How we measure it: 09-09 · 09-10 · 09-11 · 09-12 · 09-18

How we shortlisted English to Japanese translation solutions

• We shortlisted 13 solutions for Japanese: 4 in the top 8 of both COMET-Kiwi and MetricX, 4 in the top 8 of COMET-Kiwi only and 4 in the top 8 of MetricX only, and 1 added as a real-time solution (<2 sec).
• The other 31 models we got a translation from did not make the shortlist: they have automatic scores but no Intento LQA result.
• OpenAI GPT-5.6 Luna and OpenAI GPT-5.6 Sol count once with OpenAI GPT-5.6 Terra, and xAI Grok 4.20 (non-reasoning) with xAI Grok 4.20 (reasoning), as models of one family.
• The automatic metrics rank DeepL Next Gen first on both COMET-Kiwi and MetricX in Japanese.

Every model we got a translation from, as the shortlist compared it: off the shelf, without context in the request, or adjusted, with it. A model that did not make the shortlist is shown adjusted, unless off the shelf it scores higher by 0.03 or more on COMET-Kiwi. Ranks among 44 models, with each model family counted once, and the top 8 of each metric in bold. Higher is better on COMET-Kiwi, lower on MetricX. The scores rank models within this language and are not a requirement result.

How we measure it: 00-08 · 00-09

English to Japanese translation speed

• Translations into Japanese are real-time (<2 sec) from 10 models.
• None of the real-time solutions meet every Standard requirement.

Real-time models are those the shortlist counts as real-time, under 2 seconds per text across the languages we timed. The chart shows the time of each model into Japanese.

How we measure it: 12-01 · 12-02 · 12-09

How confident are we in measuring English to Japanese translation quality?

• Both pairs of automatic metrics agree in Japanese.
• The three LQA judges agree on 90% or more of the sentences for 11 of the 13 shortlisted solutions.

How we measure it: 00-07 · 07-05 · 09-02