How to use this calculator
- Enter opening portfolio value, closing portfolio value, external deposits positive, withdrawals negative, fraction of period remaining after each flow.
- 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
Weights range 0–1; matching lists and positive weighted capital required. Large flows or volatile returns can make this approximation unreliable.
Worked example
For the sample inputs shown above, modified dietz return produces a first result of approximately 16. The assumptions below explain what this result represents.
What the result means
Estimate a cash-flow-adjusted holding-period return without daily valuations.
Common questions
How is the calculation performed?
Return=(closing−opening−sum(flows))/(opening+sum(flow×remaining-period weight)).
What does the model leave out?
Weights range 0–1; matching lists and positive weighted capital required. Large flows or volatile returns can make this approximation unreliable.
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.