PlanMaker RRI Function: Investment Growth and Implied Interest Rate

RRI answers: What fixed rate per period would turn one initial amount into a given final amount over a specified number of periods? The vendor explicitly describes one payment made at the beginning and a fixed interest rate. This makes it suitable for comparing a beginning and end account value in a hypothetical single-deposit savings plan or for annualized growth of a lump-sum amount, provided there are no intermediate deposits or withdrawals. [S1]

For periodic loan repayments or savings deposits, use a financial function designed for cash-flow streams (such as RATE, PMT, or IRR) with the proper assumptions. RRI does not accept a payment stream or discount-rate guess; it solves a simpler growth equation. PlanMaker’s vendor reference specifically mentions related PERIOD and RATE. [S1]

=RRI(Per, PV, FV)

No arguments are optional. The same unit must be used throughout: if the intervals are months, the returned rate is per month, not per year. The English reference uses comma separators; locale-specific delimiter behavior has not been natively checked. [S1, S2]

Legacy identity: SoftMaker states that this function was called PCF in older versions of PlanMaker. That historical label does not establish that current versions accept both names; use the currently documented RRI spelling. [S1]

Enter =RRI(B2,B3,B4) in B5. The official manual example RRI(10,3000,5000) prints 0.05241, about 5.24%. Mathematically this is (5000/3000)^(1/10)-1 = 0.0524097791489…, obtained independently here. Format B5 as a percentage to show a readable rate; changing the display format does not change the stored number. [S1, C1]

If PV=1000, FV=1464.10, and Per=4, then:

=RRI(4,1000,1464.1)

has the independent expectation 0.10, or 10% per period. Check by reversing the calculation: =1000*(1+RRI(4,1000,1464.1))^4 is independently expected to return 1464.10 (subject to tiny floating-point display differences). This is a self-check of a rate as opposed to merely assuming the requested ending value is right. [C1]

A single amount of 1,000 ending at 800 after three annual periods implies:

=RRI(3,1000,800)

The independent compound model gives −0.0716822333, approximately −7.1682% per year. This expresses a constant equivalent rate for a loss, not a forecast and not proof that the investment decreased by precisely this percentage in each observed year. [C1]

An initial 10,000 reaching 12,100 over 24 months gives:

=RRI(24,10000,12100)

The expected monthly rate is approximately 0.00797414043, or 0.797414% per month. An independently checked expression for its equivalent annual compounded rate is:

=(1+RRI(24,10000,12100))^12-1

Expected 0.10 (10% effective annually). Do not multiply the monthly percentage by 12 and call that the effective annual rate: it would instead be a different (nominalized) quantity. [C1]

For the positive-balance compound-growth model, FV = PV × (1+r)^Per. Algebraically, the unique positive-base solution is r = (FV/PV)^(1/Per) - 1. This is independent reference mathematics, not a claim about the exact PlanMaker software algorithm or rounding path. The official vendor entry gives the input semantics and an output example, not source code for its implementation. [S1, C1]

If cash flows happen in the middle of the measurement interval, if the rate varies over time, or if balances can change sign, this model no longer describes the investment faithfully. Choose a suitable cash-flow method before treating any computed percentage as return on invested capital.

A negative expected answer, such as the 800-from-1000 example, is a meaningful compound loss when the inputs are positive and the model is appropriate. It does not imply that an application supports arbitrary negative PV/FV inputs or complex roots; no such native claims are made here.

The current official manual is for SoftMaker Office 2026 and NX. It documents RRI and explicitly mentions the older PlanMaker name PCF, and states that Excel added the function in Excel 2013. Microsoft’s own Excel RRI(nper,pv,fv) page confirms corresponding argument order and separately describes Excel’s #NUM! and #VALUE! cases. Those specific error codes are Excel evidence, not verified PlanMaker behavior. No desktop/mobile edition, localized workbook import/export, or Excel execution was performed here. [S1, E1]

• RATE addresses a different financial problem when regular payments are involved.
• FV describes future value with an assumed rate and cash-flow model.
• PERIOD is specifically mentioned alongside RATE in SoftMaker’s 2026 RRI manual entry.
• PCF is the vendor-documented legacy name of RRI.

[S1] SoftMaker Software GmbH, PlanMaker Manual, SoftMaker Office 2026 and NX, printed p. 785, entry RRI (interest for fixed-interest investments). https://www.softmaker.net/down/pm2026manual_en.pdf. Explicitly supports syntax/order/requirements, fixed one-payment model, 10/3000/5000 example, Excel-2013 compatibility statement and older name PCF.

[S2] SoftMaker, same official manual, printed pp. 64 and 461, numeric entry and region settings. Does not establish all locale-specific list punctuation.

[E1] Microsoft, RRI function (Microsoft Excel). https://support.microsoft.com/en-us/excel/functions/rri-function. Checked as Excel-specific syntax/error-reference, never as PlanMaker evidence.

[C1] Independent high-precision compound-growth calculation, 2026-10-13 UTC, of 4/1000/1464.1, 3/1000/800 and 24/10000/12100 examples. Neither spreadsheet engine was run; no screenshots, exports, native errors or edition-specific behavior were measured.