What is a language you already speak worth?
Everyone says a related language helps. This says how much, in hours, and says zero when the answer is zero.
Where these discounts come from
Transfer effects in third-language acquisition are well attested; no published coefficient exists. Values are set conservatively — shared branch gives the largest reduction, shared script a smaller one, and the total is capped so stacking several known languages cannot produce an implausible result.
The full model, and every factor it applies: how this is calculated.
How this is worked out
The model looks at how your languages relate to the target across four channels: a shared branch, a shared family, a shared script, and typological similarity between languages that are unrelated by descent. Each contributes a discount, and the total is capped so stacking several known languages cannot produce an implausible result.
It then runs the estimate twice — once with what you speak, once from English alone — and reports the difference in hours. Hours rather than a percentage, deliberately: "8% faster" sounds like a reason to choose a language, and "about 40 hours off a 500-hour project" sounds like what it is.
It reports zero, and zero is the point
Ask what Spanish does for Japanese and the answer is nothing. A tool that always finds an encouraging number is not measuring anything, and the 30% for Spanish to Portuguese only means something because Spanish to Japanese comes back empty.
Every tool here can decline to answer, and that is the most useful thing they do.
Common questions
- I studied a language for years and it says zero. Is that right?
- If the pair is unrelated, yes. What transfers between unrelated languages is the skill of having learned one — study habits, tolerance for ambiguity, knowing what a case or an aspect is — and that is genuinely valuable and does not convert into hours. The model prices linguistic relatedness, which is a narrower thing than experience.
- Why do Japanese and Korean get a discount when they are unrelated?
- Because relatedness by descent is not the only thing that transfers. Japanese and Korean share a great deal of structure — verb-final order, particles marking grammatical role, elaborate honorific systems — and a learner of one meets familiar machinery in the other. The model calls this a typological pairing and treats it as a real head start, which it is, with a coefficient that is ours rather than published.
- Can I enter a language I only half-speak?
- The model assumes B1 or above in what you list, because that is roughly where a language is internalised enough to transfer. Listing something you studied for a term will overstate your head start. If you are unsure, leave it out — the estimate errs upward, which fails more safely than the alternative.
Sources
Everything this tool rests on. The FSI baseline is published; the factors applied on top of it are ours and are marked as estimates.
- Foreign Language Training — US Department of State, Foreign Service Institute
The class-hour bands every estimate on this site starts from, and the definition of the proficiency they lead to (ILR Speaking-3 / Reading-3).
- FSI Language Difficulty Ranking — fsi-language-courses.org
Which languages sit in which band. The State Department publishes the categories as an image, so per-language assignment comes from independent reproductions that agree with each other and with the official hour bands.
- Guided learning hours — Cambridge English
The shape of the curve between CEFR levels. Cambridge publishes cumulative hours per level (A2 180–200, B1 350–400, B2 500–600, C1 700–800, C2 1,000–1,200); our level factors are normalised against the C1 band and every one lands inside its published range.
- ILR scale — Wikipedia
That no official ILR-to-CEFR crosswalk exists. Published academic tables place ILR 3/3+ at C1; others put C1 nearer ILR 4. We take the lower reading, which makes our estimates the more conservative of the two.
- Zhongwen Shuiping Kaoshi (HSK) — Wikipedia
That Hanban's claimed one-to-one HSK-to-CEFR equivalence was rejected by CEFR bodies and is disputed by the German and French associations of Chinese-language teachers, who place old HSK 6 nearer B2–C1 than C2.
This tool is free and carries no ads or affiliate links. It is funded by commission on some course links elsewhere on the site — which pages, and how that is kept out of the recommendations.
If you got something out of this and are not going to buy a course, you can buy me a coffee instead. Entirely optional, and it changes nothing about what the calculator tells you.