How to use this calculator
- Enter chronological closing prices, initial change-count window.
- Choose a display currency, then select Calculate. Results also update after a brief pause while you edit.
- Read the result with the assumptions below. Export details or save a second scenario to compare your choices.
Formula and method
Assumptions and limitations
Needs n+1 positive prices. No losses gives100, no gains gives0, flat gives50 by declared convention. Not a trading recommendation.
Worked example
For prices 10, 11, 12, 11 and 12 with a three-change window, the seed gain is 2/3 and seed loss is 1/3. After the final gain of 1, smoothed gain is 7/9 and loss is 2/9. RSI is 100 − 100/(1 + 3.5) = 77.777778.
What the result means
Calculate a reproducible Wilder-smoothed RSI from your historical closing-price series.
Common questions
How is the calculation performed?
Seed average gain/loss with first n changes; later averages=(previous×(n−1)+new)/n. RSI=100−100/(1+gain/loss).
What does the model leave out?
Needs n+1 positive prices. No losses gives100, no gains gives0, flat gives50 by declared convention. Not a trading recommendation.
Methodology and transparency
Calculation specification reviewed on 2026-10-14. Mathematical implementation is tested against independent reference fixtures. This does not imply review by a licensed financial professional. Read the testing and precision policy.
Background reference: www.fidelity.com — financial method. FinanceMath implements its own calculator.