How it works
Return = (ending − starting − net external flows)/(starting + Σ flow × remaining-days/period-days). Flow weights use actual UTC calendar days and end-of-day flow timing.
Input definitions
- Period start date
- A complete Gregorian calendar date.
- Period end date
- A complete Gregorian calendar date.
- Starting portfolio value
- Enter the value in the labeled unit.
- Ending portfolio value
- Enter the value in the labeled unit.
- CSV: date,signed external flow; positive is contribution
- Plain text; maximum 200,000 characters.
A worked example
- Period start date
- 2026-01-01
- Period end date
- 2026-01-31
- Starting portfolio value
- 1000
- Ending portfolio value
- 1600
- CSV: date,signed external flow; positive is contribution
- date,amount 2026-01-16,500
Assumptions & limits
Single-currency illustration using your entered amounts and rates, not a recommendation, approval or forecast. No automatic tax rules or market data.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Is Modified Dietz an exact money-weighted return?
No. It approximates performance using time-weighted cash flows in the denominator. Large flows and volatile returns can make it differ from IRR or a true time-weighted calculation.
How does Modified Dietz investment return work?
Return = (ending − starting − net external flows)/(starting + Σ flow × remaining-days/period-days). Flow weights use actual UTC calendar days and end-of-day flow timing.
What are the limits of Modified Dietz investment return?
Single-currency illustration using your entered amounts and rates, not a recommendation, approval or forecast. No automatic tax rules or market data.