PlanMaker PERIOD Function: Calculate Investment Growth Time

• Introduced: Documented by the PlanMaker 2010 manual; the first introduction release is unknown.
• Availability: Listed in the 2026/NX English reference. No final supported-version endpoint is established.
• Scope: Versioned PlanMaker documentation; separate desktop/mobile introduction dates and execution parity are not established here.
• Checked: October 14, 2026, against the official PERIOD reference. Examples independently calculated; no native PlanMaker test.

=PERIOD(Rate, PV, FV)

All three arguments are required. PERIOD describes a single payment at the beginning earning a fixed rate. Its output is a number of periods, which may be fractional; it is neither a calendar date nor a payment amount. There is no payment-stream, timing or day-count parameter.

Use a decimal rate such as 0.06 or a percentage such as 6%, not the number 6 for six percent. Match the period unit to the rate. A monthly rate produces months; an annual rate produces years. The formulas below follow the English reference’s comma notation. If your editor uses another separator, retain the same argument order.

In a blank worksheet, enter these labels and numeric inputs:

Put =PERIOD(B2,B3,B4) in B6. Expect approximately 8.7666929107 years, matching the vendor’s rounded 8.76669. Format B6 as a number rather than as a percentage.

Check the result by putting =B3*(1+B2)^B6 in B7. It should reproduce 5000, apart from small floating-point differences. Keep the full B6 result in this check; do not replace it with the rounded display value 8.77.

For positive balances and a nonzero rate greater than −100%, the compound model rearranges to:

Number of periods = LN(FV/PV) / LN(1+Rate)

This equation independently explains the examples. It does not specify PlanMaker’s internal implementation or every invalid-input error.

Leave A:B intact. Enter the following numeric inputs in D2:F4, with headers Rate, Initial amount, and Target amount in D1:F1. Put =PERIOD(D2,E2,F2) in G2 and fill to G4.

Row 2 reverses four periods of ten-percent growth. Row 3 is a doubling-time calculation. Row 4 models a constant five-percent loss per period until the balance falls to 8,000; it is not a positive-return investment example. The model uses positive starting and ending balances in every row.

The official example’s result lies between eight and nine years. In D7, enter =B3*(1+B2)^8; expect 4781.5442235925. In D8, enter =B3*(1+B2)^9; expect 5068.4368770081.

If the hypothetical account can only be evaluated at complete annual anniversaries, year 9 is the first anniversary at or above 5,000. The fractional result alone does not promise that a real contract credits interest or permits withdrawal at exactly that fraction of a year. Establish those terms separately.

For an equivalent monthly compound model, put =(1+B2)^(1/12)-1 in D10. Expect approximately 0.00486755056534, or 0.4867550565% per month. In D11, enter =PERIOD(D10,B3,B4); expect 105.2003149287 months. =D11/12 in D12 returns the original 8.7666929107 years.

Dividing 6% by 12 would instead create a different compounding assumption. The monthly rate above was chosen specifically so twelve monthly periods reproduce the original 6% annual growth factor.

SoftMaker explicitly warns that PERIOD is not an Excel function. Saving a workbook in Excel format replaces its PERIOD calculations with their current fixed results. Those values will not respond to changed inputs as a PERIOD formula would.

The same reference gives this compatible alternative:

=NPER(Rate,0,PV,-FV)

For the main worksheet, put =NPER(B2,0,B3,-B4) in D14. Expect the same 8.7666929107. The second argument is zero because there are no regular payments; the minus sign before the target balance follows NPER’s cash-flow convention. Do not omit it merely because PERIOD itself takes two positive balances.

Keep the original workbook and inspect a saved copy’s formulas as well as its displayed values. A matching value immediately after export does not prove that the formula still recalculates.

• The result looks like a percentage: format it as a number of periods.
• The wrong time unit appears: check whether the input rate is monthly, quarterly or annual.
• There are regular contributions: PERIOD’s one-payment model does not represent that cash-flow pattern; use NPER with explicit payments and timing.
• The rate is zero: the logarithmic rearrangement above divides by zero; a growing target cannot be reached under zero growth. The function reference does not establish the exact application result for every zero-rate case.
• Balances are zero, have opposite signs or the rate is at most −100%: do not apply the positive-balance examples blindly. Exact error tokens, coercion and unusual domains are not enumerated by the cited entry.

Use RRI for the inverse question: the fixed rate needed to reach a target in a stated number of periods.