IPMT Function (Gnumeric)

Create a blank worksheet and enter these values without rounding intermediate calculations:

The formula arguments use a periodic interest rate because the Gnumeric implementation compounds rate each period. Do not pass 6% directly as the rate for a monthly twelve-period example: 6%/12 is the intended illustrative monthly rate here. The sample uses a nominal annual rate evenly split into 12 monthly periods; an effective annual 6% rate would instead need (1+6%)^(1/12)-1. The cash-flow sign is negative for repayments, because the present-value loan receipt is positive. This sign convention is visible in the upstream formula. [G1, G3]

How outputs were checked: Values were independently calculated with decimal arithmetic from the formula shown by Gnumeric’s public source. They are expected worksheet results, not observed output from a running Gnumeric application. Display rounding is to two decimals; do not round formula cells to two decimals when testing reconciliation. [G3]

=IPMT(B5,1,B4,B2,B6,B7) should display -60.00 for the first month because the month begins with a loan principal of 12,000 and the illustrative rate is 0.005 per month: -12000 × 0.005 = -60. In month 6, the corresponding independent result is approximately -35.435652759278 (display -35.44). The interest charge declines for the example’s ordinary end-of-period amortization because principal is being repaid. [G3]

For default type=0 and fv=0, the source computes pmt0=PMT(rate,nper,pv,0,0) and then obtains the interest amount for per from the accumulated balance. The implementation’s direct expression is:

IPMT = -(pv*(1+rate)^(per-1)*rate
       + PMT(rate,nper,pv,fv,0)*((1+rate)^(per-1)-1))

When type=1, the same source divides that calculated interest by 1+rate rather than directly transferring another application’s period-1 interest convention. For accurate beginning-of-period schedules, validate the actual deployment in native Gnumeric. The worked example deliberately sets type=0. [G3]

Period selection and zero-interest checks

The source’s period-bound error handling is verified by code inspection; the numeric amounts are independent calculations. No native execution was performed. [G3]

With the inputs from the table above, create the following headers in row 11: A11 = Period, B11 = Total payment, C11 = Interest, D11 = Principal, and E11 = Remaining balance. Then enter:

Copy B12:E12 through row 23, and A13 through row 23. Expect B12 to remain near -1032.80 each row, while the interest amount moves from -60.00 in period 1 to approximately -5.14 in period 12; the principal amount moves from approximately -972.80 to -1027.66. The unrounded balance in E23 should be approximately zero. The reconciliation check =B12-(C12+D12) should also be approximately zero. [G1, G3]

Use the actual full-precision numeric cells for sums. Formatting the results as currency does not round the underlying amortization, whereas physically rounding each row’s value would introduce a small cumulative difference. The model assumes a fixed rate and fixed payment schedule; changed rates, real lender day-count rules, additional payments and fees require an adjusted model.

• Gnumeric, not Excel: These are Gnumeric formulas. The official Gnumeric 1.12 Finance manual documents the names and argument order. Gnumeric’s public catalogue labels the function a Complete implementation with Basic upstream testing; that status does not verify this tutorial’s specific cells or cross-application import. [G1, G2]
• Source check: The implementation and registration were reviewed in plugins/fn-financial/functions.c from the checksum-verified official Gnumeric 1.12.62 source archive. Source inspection does not establish execution or every packaged platform’s behavior. [G3]
• Release/platform scope: The GNOME 1.12 release directory establishes availability of Gnumeric 1.12 source releases, but no installed Linux, Windows or macOS Gnumeric build was started here. Packaging, plugin activation, and localized parsing were not tested. [G5]
• Payment timing: The official manual documents type=0 for payments at the end of a period (default) and type=1 at the beginning. Gnumeric source maps a nonzero numeric type to 1, but use explicit 0 or 1 for clarity. For type=1, IPMT is specifically computed from its type-0 helper and divided by (1+rate); do not substitute another spreadsheet application’s assumptions. The example table above uses only type=0. [G1, G3]
• Locale: The manual’s formulas are shown using commas. Gnumeric’s localization documentation explains the environment’s locale-dependent conventions; the syntax in a configured installation should be confirmed in that installation before promising copied formulas will parse unchanged. [G1, G4]

• PMT — related financial calculation.
• PPMT — principal component.
• CUMIPMT — related financial calculation.
• PV — related financial calculation.
• ISPMT — related financial calculation.

Sources checked 13 October 2026 (UTC). The bracketed evidence keys above refer to the following claim-level primary sources:

• [G1] Gnumeric 1.12 official Finance function reference — search within the manual for this function’s heading; confirms function purpose, argument order, type interpretation, and official related functions.
• [G2] Gnumeric official function catalogue — establishes catalogue registration and upstream Complete / Basic classification, not runtime proof.
• [G3] GNOME Gnumeric upstream financial-functions C source, from the verified 1.12.62 source archive — search gnumeric_pmt, gnumeric_ipmt, gnumeric_ppmt, and calculate_pmt / calculate_ipmt; confirms optional arguments, defaults, repayment arithmetic, bounds checks, and payment-timing source behavior.
• [G4] Gnumeric official Languages and Locales guidance — locale context, not a test of the current operating system.
• [G5] GNOME official Gnumeric 1.12 source-release directory — release provenance, not application execution on the user’s platform.

Validation scope: Official manual and verified 1.12.62 source were reviewed; listed examples were independently calculated. Native Gnumeric execution, screenshots and locale/platform regression tests were not performed. The implementation compounds the supplied rate once per payment period, which controls the 6%/12 conversion. [G1, G3]