The Foreign Service Institute (FSI) of the U.S. has measured for 70 years how many hours it takes an adult to reach B2/C1 in each language. For a Brazilian to achieve professional fluency in English: 600 to 750 hours. This equals 1 year and 8 months with 1 hour a day, or 10 months with 2 hours a day. In this post, I show the complete FSI table, the graph of hours per language, and why most people who "study for years" haven't even reached 200 real hours.
Look, if you've studied English, stopped, returned, stopped again, and have that feeling of "but I’ve studied so much..." — maybe you’ve studied much less than you think. The right question isn’t "how long have I studied?", it’s how many real hours have I accumulated. And for that question, there is an official answer.
The Foreign Service Institute (FSI) — the language school of the U.S. Department of State — has been training American diplomats in foreign languages for over 70 years. They have the most respected dataset in the world on how long it takes an adult to reach each level in each language. This number, for a Brazilian to reach professional fluency in English, is 600 to 750 hours.
In this post, I show where this number comes from, the complete FSI chart, and what it means in your real routine. The Lanna (Brazilian language learning platform with AI) automatically tracks study hours for you to see where you are on this curve.
The official number: 600-750 hours
For an adult to reach B2/C1 in English from Portuguese, it takes 600 to 750 hours of focused study. This number comes from the official FSI table, based on decades of data from adult diplomats with intensive instruction and a clear goal: professional proficiency (General Professional Proficiency, S-3/R-3 on the ILR scale, equivalent to B2/C1 of the CEFR).
The FSI measures from English, but the reciprocity between closely related languages is symmetrical: if an English speaker needs 600-750h to achieve B2 in Portuguese, a Brazilian needs something very close to achieve B2 in English. It’s the number validated over the last 70 years by tens of thousands of students.
The FSI graph: hours per language
Looking at the graph, English is in a comfortable position: among the 7 easiest languages in the world for Brazilians. Almost 4 times faster than Arabic or Japanese. And only slightly slower than Spanish — because it has more Germanic vocabulary (which does not come from Latin) and a very different phonology.
What this means in your routine
The important point: 15 minutes a day doesn't work. It's not due to lack of effort — it's math. In 15 minutes, the brain barely enters the deep language processing state before you close the app. And in 6 years, forgetting (Ebbinghaus curve) eats away what you've learned faster than you add new content.
The ideal point for working adults is 1 hour a day. Sustainable, enough to activate long-term memory, and gets you to B2 in less than 2 years. Those who do 2 hours reach it in 10 months — but it requires military discipline and is hard to maintain for months without burning out.
Why most people "study for years" and don’t get there
Because "studying for years" is not the same as "having 600 accumulated hours". Let's do the math: if you took Wizard classes 2x a week for 2 years (1h per class), that's 200 hours. If you did Duolingo for 10 minutes a day for 1 year, that's 60 hours. Adding the two: 260 hours. You "studied English for 3 years" — but you are only at 35-40% of the FSI hours.
This is the main reason Brazilians get frustrated. It’s not a lack of talent, it’s a lack of real hours. The good news is that you can speed up.
How to squeeze more value per hour
- Comprehensible input — material at the right level (Krashen). If it’s too easy, you don’t learn; if it’s too hard, you get tired. Complete guide to comprehensible input.
- Active production every day — speaking and writing, not just listening and reading. Voice conversation with AI solves the problem of "there's no one to practice with".
- SRS for vocabulary — SM-2 cuts forgetting in half. Each word reviewed at increasing intervals (1d, 3d, 7d, 15d, 30d) sticks. How to use SRS correctly.
- Partial immersion — phone in English, Google in English, series in English with English subtitles. Adds 30-60 min/day "for free" without you feeling it.
- Stop translating in your head — when the brain processes directly in English, each hour becomes double the progress. How to stop mentally translating.
Where the FSI fails (the honest critique)
The number of 600-750 hours is validated, but it has important assumptions that most people do not meet:
- Motivated and adult learner. A diplomat studies because their career depends on it. Any adult studies because "it would be nice". Motivation greatly alters actual time.
- Intensive and structured instruction. The FSI has teachers, curriculum, material, and a clear goal. Those who study alone with random apps don’t have that.
- Focus on a single language. A diplomat studies only that language for 6 months. Those who study 30 min of English 3x a week between work and family have lower hourly yield.
- B2/C1 goal, not C2. To reach native level (C2) or indistinguishable pronunciation, thousands of hours more are required.
In practice, an organized self-taught Brazilian takes 800-1000 hours to solidify B2. But the FSI number remains the best benchmark available.
Frequently Asked Questions
How many hours for total fluency like a native?
There is no reliable estimate — some studies mention 10,000+ hours. But for practical purposes, B2/C1 is the point where the language "unlocks".
Do you count study hours or consumption hours?
Count hours of focused exposure — reading an article attentively, listening to a podcast trying to understand, speaking with AI. Background music while doing something else doesn’t count.
Does age change the number?
Slightly. An adult may need 10-20% more hours than an immersed child, but the difference is less than one might think. Do adults learn languages worse?
Can I jump to C1 faster if I already have B1?
Yes — those who already have 300-400 hours of passive base accelerate activation significantly. The last 200 hours are the most productive if you focus on production and niche.
Is the FSI reliable for other languages besides English?
Yes — it is the global gold standard. Every serious language school uses the FSI table as a reference.
Start counting today
Write down an honest estimate of how many real hours you have studied English in your life. Include classes, series with English subtitles, reading, apps. It will probably be much less than you thought. Now calculate how many hours you need to reach 600. If it’s 400 and you study 1h/day, that’s 14 months. If it’s 500, that’s 17 months. If it’s 50, that’s 18 months. In all cases, it’s less than it seems — as long as you don’t stop.
Count your hours, get there
Lanna automatically tracks your real study hours (listening, speaking, reading, writing) and shows you where you are on the FSI curve towards 600 hours.
Try Lanna for free