Evidence-first money workflow · Finance & Business
Portfolio Return CSV Analyzer
Calculate chained time-weighted portfolio return from CSV periods while separating external cash flows, ending value, and simple value gain.
- 1Prepare
- 2Analyze
- 3Review and export
Prepare the evidence
Paste the documented CSV schema or choose a local CSV file. Nothing is sent to Nirmion.
Review the analysis
Summary metrics lead back to the rows that support them.
Method and interpretation
How to use Portfolio Return CSV Analyzer
Use this portfolio return calculator when deposits and withdrawals make a simple beginning-to-ending percentage misleading. It calculates a chained time-weighted return from consecutive periods and keeps every opening value, external flow, ending value, and period return visible. It is suited to spreadsheet audits and account reviews where periods can be split around meaningful cash flows.
Prepare the input
Create one row per measurement period with a unique end date, opening portfolio value, signed external flow, and ending value. Contributions are positive; withdrawals are negative. This version assumes the flow is available at the period start. For better precision, divide a month into subperiods around large flows or use valuations immediately before each contribution or withdrawal.
Check the worked example
The worked example starts at USD 10,000, includes contributions in January and March, no flow in February, and a withdrawal in April. Each row calculates return after adjusting for that row’s external flow. The chained result multiplies the period growth factors instead of averaging the percentages.
Read the evidence
Time-weighted return links each period’s investment result and reduces the effect of how much money you added or removed. Net external flows show capital movement, while simple value gain equals ending value minus the first opening value minus flows. Large period returns are flagged for review because they often reveal a sign error, a missing cash flow, or inconsistent valuation dates rather than exceptional performance.
Calculation method
Period return = ending value ÷ (opening value + external flow) − 1 under the documented start-of-period flow assumption. Chained time-weighted return = product of (1 + each period return) − 1. Simple value gain = last ending value − first opening value − sum of external flows. Results retain full precision until display.
Review Portfolio Visualizer’s documented portfolio backtesting capabilities
Questions this workflow helps answer
Use these questions to confirm that this tool matches the task you need to complete.
- How do I calculate time-weighted portfolio return from a CSV?
- How should deposits and withdrawals be separated from investment performance?
- Why does my portfolio value gain differ from my time-weighted return?
Limits and decision boundary
The method needs consistent valuations and correctly timed flows. It does not calculate an internal rate of return, benchmark-relative return, volatility, drawdown, taxes, dividends outside the portfolio value, or annualization. If a flow occurs midperiod, the start-of-period assumption can distort that period. Brokerage statements may use a different standard.
Common mistake
Do not record investment income or market gains as external contributions when they remain inside the portfolio. External flows are money crossing the portfolio boundary; internal dividends and sales should already be reflected in ending value.
Your pasted values and selected CSV files are processed in this browser tab. This workflow does not connect to a bank, save a budget, or provide financial, tax, legal, or investment advice.
Questions about this workflow
Is this an XIRR calculator?
No. XIRR is money weighted and depends on exact cash-flow dates. This page calculates chained period returns under a disclosed flow-timing rule.
Should consecutive opening values equal prior ending values?
Usually, unless the next row begins a different valuation boundary. Investigate gaps because they may indicate missing periods or flows.
Can I mix daily and monthly periods?
The arithmetic can chain them, but interpretation and any later annualization require consistent period definitions.