Vocabulary Retention Calculator
Spaced-repetition words retained over time.
Enter your values
ⓘ Live results
Results
- Words retained
- 360
- Words introduced
- 900
- Retention rate
- 40%
- Memory strength (days)
- 27.6
Quick answer
Retention decays exponentially, and each review resets the curve to a slower decay.
Retained = new × e^(−days ÷ strength)
How to use the Vocabulary Retention Calculator
- 1Enter how many new words you add each day.
- 2Enter how long you have been studying.
- 3Enter typical reviews per word.
Worked example
Using the values the calculator loads with:
Inputs
- New words per day15
- Days studied60
- Reviews per word4
Results
- Words retained360
- Words introduced900
- Retention rate40%
- Memory strength (days)27.6
Frequently asked questions
Why do reviews matter so much?
Each successful recall lengthens the interval before you forget.
Is this exact?
No — it models Ebbinghaus's curve to show trends, not guarantees.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.