IRR Calculator

Before you calculate

Use this calculator when cash-flow timing matters and a simple start-to-end ROI is too limited. Use fixed recurring cash-flow mode for one repeated deposit or withdrawal pattern plus an ending balance. Use irregular annual cash-flow mode for project-style year-end cash flows. Use ROI for a simpler amount-invested and amount-returned comparison, Average Return for period returns or account cash-flow weighting, Payback Period for recovery timing, and Investment for fixed-return contribution projections.

Formula summary

The calculator builds a signed timeline where outflows are negative and inflows are positive. Fixed mode converts Holding years plus Holding months divided by 12 into total holding years, maps the selected frequency to periods per year, rounds the recurring period count, records the initial investment at time zero, records deposits as recurring outflows or withdrawals as recurring inflows at the selected beginning or end timing, and records ending balance at the holding date. Irregular mode records Irregular initial investment at time zero and each non-zero annual cash-flow field at the end of that year. The app then searches annual rates from -99.99 percent to 1000 percent for the first NPV sign change, bisects that bracket, and reports IRR, NPV at IRR, total cash in, total cash out, net cash flow, holding years used, and cash-flow count.

Worked example

Example: fixed monthly withdrawals and irregular annual cash flows

With the default fixed-mode inputs, a $10,000 initial investment, a $15,000 ending balance after 2 years and 6 months, and $100 monthly withdrawals at the end of each month create 32 non-zero cash flows. The result is 29.77 percent IRR, $0 NPV at IRR after rounding, $18,000 total cash in, $10,000 total cash out, $8,000 net cash flow, and 2.5 holding years used. In irregular annual mode, the default $50,000 initial investment, -$10,000 in year 1, $30,000 in year 2, and $50,000 in year 3 create 4 non-zero cash flows and report 12.45 percent IRR, $0 NPV at IRR, $80,000 total cash in, $60,000 total cash out, and $20,000 net cash flow.

The rate changes because IRR is driven by both amount and timing. The cash-flow totals help explain scale, while NPV at IRR checks that the solved rate balances the modeled timeline.

Assumptions

• Fixed mode uses one repeated cash-flow amount and one ending balance. Deposits are modeled as investor outflows, withdrawals are modeled as inflows, and the frequency choices map to annual, semiannual, quarterly, monthly, semimonthly, biweekly, or weekly periods.
• Irregular mode uses annual year-end cash-flow fields from year 1 through year 50, not a dated XIRR schedule with exact calendar dates. The solve returns 0 when the modeled timeline does not include at least one positive and one negative cash flow.
• Cash flows with more than one sign change can have multiple mathematical IRRs, and this app reports the first bracketed root it finds in its practical search range or falls back to the annualized cash-flow solve. The calculator does not model changing contribution amounts, fees, taxes, inflation, reinvestment rates, required returns, project risk, market volatility, provider performance reporting, MIRR, or NPV at a separate hurdle rate, and results are educational estimates rather than financial, tax, legal, lending, investment, project-approval, or regulated advice.

Common mistakes to avoid

• Treating IRR as the same thing as total profit or simple ROI. A smaller scenario can show a higher IRR while producing less total cash profit.
• Using fixed mode for changing cash-flow amounts, or using annual irregular mode when exact calendar dates matter. A dated XIRR model is a different calculation boundary.
• Reading IRR as a forecast, product return, provider statement, approval decision, or recommendation. Compare scale, timing, risk, fees, taxes, and other metrics before relying on any one estimate.

Methodology and sources

This calculator is an original implementation based on documented formulas, app-specific assumptions, deterministic fixtures, edge cases, rounding policy tests, and internal validation. It is not copied from a single source.

Outputs are checked with deterministic fixtures, edge cases, rounding policy tests, and internal independent comparator checks where overlapping outputs are available. The result remains an educational estimate, not a quote, approval, tax answer, or personalised advice.

Formula version 2026.05.22-generic-irr. The version marks the calculation logic and validation fixture set used for this estimate.

• Microsoft IRR and XIRR documentation can support supplemental spreadsheet context for regular-interval versus dated cash-flow semantics, positive and negative cash-flow requirements, and iterative solving, but it does not define this app's original root-search implementation.
• Investor.gov Investment Products, What is Risk, and Understanding Fees materials should be used before copy discusses investment-product features, risk, return interpretation, liquidity, fees, costs, diversification, fraud, or real-world account outcomes.
• SEC, FINRA, FCA, MoneyHelper, product documents, prospectuses, fee disclosures, brokerage statements, provider reports, tax authorities, accounting standards, lender materials, local regulators, and legal sources should be used before copy frames generic IRR math as formal performance reporting, time-weighted return, money-weighted reporting standard, project approval, regulated product comparison, tax treatment, accounting treatment, legal claim, product-specific guidance, or jurisdiction-specific advice.

Estimate only

The result is educational and is not financial, tax, legal, lending, investment, or regulated advice. Real provider terms, fees, rates, taxes, and personal circumstances can change the final answer.

Formula and help: read the full irr calculator methodology notes.

Related reading

• How Calcs.finance validates calculator formulas
• Estimate limitations and not-advice disclaimer

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