Irish Calculators
Saving & investing

IRR Calculator for Periodic Cash Flows

Calculate a return per cash-flow period, then see its annual equivalent at your selected frequency. Use XIRR for actual dates, and review any warning about absent or multiple roots.

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Your numbers

First amount occurs at time zero. Enter up to 60 comma-separated amounts; use 0 for an empty period.
Your figures stay on this device.

How the calculation works

IRR finds a return per equal cash-flow interval. The calculator also offers an annuity mode for a purchase followed by equal end-of-period receipts, keeping the periodic rate separate from its annual compound equivalent.

Solve sum[CF[t] ÷ (1+r)^t] = 0. Annual equivalent = (1+r)^(periods per year) − 1.

  1. Place cash flows on the schedule

    General mode uses successive equal intervals; annuity mode places the initial purchase first and each receipt at a period end.

  2. Solve the periodic return

    Discount each later flow back to time zero and find the rate that makes the sum balance. Mixed-sign patterns can produce multiple roots, which are disclosed instead of reduced to one unexplained number.

  3. Annualise with the stated frequency

    Raise one plus the periodic rate to the number of periods per year, then subtract one. Multiplying the rate by frequency would give a different convention.

Worked example: Check IRR per cash-flow period

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example is an initial outflow of 1,000 followed by 1,100 one period later. The balancing periodic rate is 10%; with one period per year, the annual equivalent is also 10%.

Cash-flow mode
Individual equal-period cash flows
Cash flows at equal intervals
-1000,1100
Cash-flow periods per year
1

Expected result

IRR per cash-flow period
10%
Worked example: Check IRR per cash-flow period

Sample inputs demonstrate the method. They are not a forecast or product offer.

Cash-flow mode
Individual equal-period cash flows
Cash flows at equal intervals
-1000,0,1210
Cash-flow periods per year
1

Expected result

IRR per cash-flow period
10%

Understanding your result

The periodic IRR is only annual when one period is a year. A monthly cash-flow list requires a frequency of twelve for its annual effective equivalent.

Actual payment dates that do not fit equal intervals belong in XIRR. IRR does not read calendar gaps from the number of rows or from descriptive labels.

Questions you might have

What does the result include?

Find the internal return per equal cash-flow period, and annualise it only with a declared frequency.

Which limits should I check?

Up to 60 individual flows or 1,200 equal end-of-period annuity receipts; per-period search range −99.9999% to 99,999,900%. Use XIRR for actual dates.

Choosing the right inputs

Cash flows at equal intervals
The first amount occurs at time zero. Preserve empty intervals with zero entries; deleting them changes the timing of every later flow.
Cash-flow periods per year
Enter the number of cash-flow periods per year. This is used for annualisation, not to insert additional receipts between the values entered.
Cash-flow mode
Use annuity mode for equal receipts over many periods, with an optional additional final receipt. It supports a different input pattern from a general flow list.

Common mistakes to avoid

  • Do not omit a zero-payment month from a monthly series.
  • An annuity's implied return is different from projecting its accumulated future value.

Assumptions to check

  • Up to 60 individual flows or 1,200 equal end-of-period annuity receipts; per-period search range −99.9999% to 99,999,900%. Use XIRR for actual dates.
  • All calculations run on your device. Figures are scenarios based on your inputs, not investment recommendations.

Sources and method

Read our calculation and testing approach.