Modified Dietz Return Calculator
Estimate a flow-adjusted period return from opening/closing values and dated signed external cash flows.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Weight each flow by its remaining fraction of the date interval. Divide value change excluding net flows by opening value plus weighted flows.
Dietz=(closing−opening−Σflows)/(opening+Σ(flow×remaining interval fraction))
Worked example
Opening 1000, closing 1650 and a 500 deposit halfway through a 30-day interval give adjusted gain 150, weighted capital 1250 and estimated return 12%.
Assumptions and input details
An approximation using available valuations, not an exact time-weighted return or IRR. Date interval must be positive; weighted capital must be positive. Opening-date flows have weight 1 just after opening valuation; closing-date flows have weight 0 and are included in closing value. Intermediate dates use elapsed calendar days. Large flows or volatile paths can make the approximation poor. All results are before tax unless the entered cash flows already include it. No national rules, investment recommendations or actual market forecasts are supplied. No live market data or national tax rules are inferred. Enter consistent amounts in one currency unless explicitly stated otherwise.
References: GIPS: return calculation methodology
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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