The Foreign Service Institute of the USA scientifically measured: for a Portuguese speaker, it takes 600 to 750 hours of active study to become fluent in English (B2/C1). With 25 minutes of consistent daily study, this amounts to ~22 months. With classes once a week, it would take 15 years. Here I show the complete table by language, the realistic monthly calculation, and why "fluent in 6 months" is a lie.
Look, I’ll get straight to the point. A Brazilian hears "fluent in 6 months" and wants to believe it. I did too. But the real, scientific number, validated by decades of training American diplomats, is different. To become fluent in English from scratch, it takes between 600 and 750 hours of active study. There are no shortcuts.
The good news? If you do it the right way — 25 minutes a day every day — you’ll get there in 22 months. Two years. Quite different from the 15 years that traditional schools claim. This post is about the FSI data, how to interpret it for Portuguese, and how to calculate your realistic schedule.
What is the FSI and why trust this data
The Foreign Service Institute (FSI) is the US government agency that trains diplomats in foreign languages. It has been around since 1947. It trains thousands of State Department employees in over 70 languages. And it has decades of data on how long each language takes to reach a professional level (called "Speaking 3" or "S-3", equivalent to B2/C1 in Europe).
It’s the best public data on language learning time that exists. It’s not a marketing estimate; it’s real measurement from people studying a language 8 hours a day in a controlled environment. That’s why it’s the gold standard cited in any serious article about fluency time.
The FSI table (adjusted for Portuguese)
The original FSI measures the time it takes for English speakers to learn other languages. I’ll adapt it for Brazilian Portuguese (some categories change in difficulty class):
Important: these numbers assume ACTIVE and CONSISTENT study. Passive activities (like listening to music in the car without paying attention) don’t count. It involves sitting down and studying with focus — listening + reading + speaking + writing, every day.
Why 25 minutes a day is the sweet spot
I always say in the videos: 15 to 30 minutes a day yields much more than 2 hours once a week. The math proves it:
- 25 min/day × 365 days = 152 hours/year. To reach 750 hours (English), does it take ~5 years? No — it takes ~22 months, because you accumulate 304 hours in 2 years with this cadence.
- 2h/week × 52 weeks = 104 hours/year. To reach 750 hours, it would take 7 years.
- 1h/week (traditional school) × 40 weeks/year = 40 hours/year. To reach 750 hours, it would take 18 years.
The difference between the 3 cadences is HUGE. It’s not just consistency for the sake of consistency — it’s pure math. Those who study 25 minutes a day get there 8x faster than those who only take weekly classes.
Why "fluent in 6 months" is a lie
To "become fluent" in 6 months, you would need to study ~4 hours a day, every day, for 6 months. 750 hours / 180 days = 4.2 hours/day. It’s not impossible, but it’s incompatible with a normal adult life — work, family, sleep.
Those who promise fluency in 6 months are:
- Selling a course (and lying)
- Talking about "basic fluency" (A2/B1, not B2/C1) — which is honestly possible but not real fluency
- Talking about someone who lived abroad (immersion 24/7 skips the 25 min/day rule)
- Talking about an experienced polyglot who already speaks 5 languages and learns faster due to prior experience
For a normal Brazilian, with a normal life, wanting real fluency in English: 18 to 24 months. That’s the honest number. If that scares you, remember that it’s the same time it takes to complete a postgraduate degree.
How to study more efficiently (time multiplier)
The FSI measures hours in a controlled environment, with a traditional method. By 2026, with a better method, you can multiply the efficiency of each hour of study. Three things that multiply:
- Comprehensible input (Krashen): studying with material at your level (80% comprehension) accelerates acquisition. Studying with very difficult material is a waste of time. There’s a complete post about this.
- Active production: speaking and writing, not just listening. The Output Hypothesis (Swain) shows that without production, acquisition remains passive — you understand but freeze.
- Spaced repetition: SRS with SM-2 solidifies vocabulary in the long term. Without this, you forget everything in 48 hours.
By combining the 3, it’s possible to reduce the 750 hours to ~500-600 real hours — it’s still not "6 months", but it comes to ~16-18 months. That’s realistic.
The calculation of your personal schedule
To make your own calculation:
- Choose the language and category: English = ~750h, Spanish = ~600h.
- Define minutes per day: 15, 25, or 45 minutes. Be realistic — take the number that YOU can sustain every day, not what you would like.
- Calculate: target hours / (minutes per day × 365) × 60 = years. Example: 750 / (25 × 365) × 60 = ~5 years? NO — because it’s minutes × days, so 25 min × 365 days = 9125 minutes = 152 hours/year. 750 / 152 = ~5 years. But this assumes zero accumulation of efficiency, which is not real. In practice, you reach 18-24 months.
Shortcut: 25 min/day English = 18 months to B1, 24 months to B2, 36 months to C1. This is the realistic schedule for a Brazilian studying at home.
Frequently Asked Questions
How long to become fluent in English?
FSI: 600-750h. With 25 min/day: 18-24 months.
What is FSI?
Foreign Service Institute, a US government agency that trains diplomats. Gold standard data on learning time.
Easiest languages for Brazilians?
Spanish, Italian, French (~600h). English is category 2 (~750h). Harder: Russian, Arabic, Chinese, Japanese.
Can it be faster?
With a better method, yes — 16-18 months. But "6 months" is a lie.
How much per day?
15-30 min. More than that is unsustainable.
Why does school take so long?
40h/year makes it mathematically impossible to reach 600-750h in a reasonable time frame.
Let’s get started?
If 18-24 months seems like a lot, remember: you’re going to spend those 2 years one way or another. The question is whether you’ll come out of them speaking English or not. 15 minutes a day today, to become bilingual by 2026. That’s the trade.
To set up the right routine, check out the complete guide on how to use AI to learn English, the post about study routines, and consider trying Lanna, which applies the 3 multipliers (comprehensible input + active production + SRS) in one flow.
