Vocabulary Growth Calculator
Estimate how large your vocabulary will be after a set study period. Enter your current word count, daily learning rate, and number of days to project your future vocabulary size.
About this calculator
Vocabulary growth follows a simple linear model when you learn a consistent number of new words each day. The formula is: Future Vocabulary = currentVocab + (newWordsPerDay × days). For example, if you already know 2,000 words and learn 10 new words daily, after 30 days you will know 2,300 words. This model assumes perfect retention, so real-world results may be slightly lower due to forgetting. Language researchers often pair this kind of projection with spaced-repetition retention rates to get a more realistic estimate. Still, the linear formula is a useful baseline for setting study goals and measuring progress milestones.
How to use
Suppose you currently know 3,000 words, you learn 15 new words per day, and you want to project growth over 60 days. Step 1 — Enter 3,000 in Current Vocabulary. Step 2 — Enter 15 in New Words per Day. Step 3 — Enter 60 in Number of Days. Step 4 — The calculator computes: 3,000 + (15 × 60) = 3,000 + 900 = 3,900 words. After two months at that pace, your projected vocabulary is 3,900 words.
Frequently asked questions
How many new words per day do you need to reach B2 level in a language?
B2 fluency in most languages requires roughly 4,000–8,000 words. If you start from zero and target 6,000 words in one year (365 days), you need to learn about 16–17 new words per day. Using the formula, 0 + (17 × 365) = 6,205 words. Consistent daily practice combined with spaced repetition gives the best retention, making that rate very achievable.
Does this vocabulary growth calculator account for forgetting?
No — the formula currentVocab + (newWordsPerDay × days) assumes you retain every word you learn, which is an idealized scenario. In reality, the Ebbinghaus forgetting curve means you will lose some words without review. To compensate, language learners typically use spaced-repetition systems like Anki, which can push real retention above 90%. You can adjust newWordsPerDay downward to build in a forgetting buffer.
What is a realistic number of new words to learn per day for an adult?
Research suggests adults can comfortably acquire 10–20 new words per day with active study, and up to 30 with intensive immersion programs. Passive exposure through reading and listening adds further vocabulary over time. For sustainable long-term learning, most polyglots recommend 10–15 words per day combined with daily review sessions. Quality of study (context, example sentences, spaced repetition) matters more than raw quantity.