PlanMaker DECIBEL: Compare Power Ratios and Reference Levels
Calculate decibel ratios in PlanMaker with explicit references, reversed-ratio checks, chained changes and the documented Excel export limitation.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
DECIBEL converts a ratio into a decibel value. In PlanMaker, the quantity being compared comes first and its reference comes second. A tenfold ratio gives 10 dB; equal quantities give 0 dB; a smaller positive numerator gives a negative result.
The reference matters. Comparing 1000 with 10 is a different calculation from comparing 1000 with the function’s default reference of 1.
Availability and version history
- Introduced: Documented by the PlanMaker 2010 manual; the first introduction release and date remain unknown.
- Availability: Documented in PlanMaker 2026. That checked version is not a final supported-version endpoint; the Excel export restriction is not a retirement notice.
- Scope: The current reference belongs to the PlanMaker 2026/NX manual family. Individual FreeOffice and mobile-build availability are not established here.
- Checked: October 14, 2026, against the official DECIBEL reference and historical manuals. Examples were independently calculated; no native PlanMaker execution was performed.
Syntax and the reference quantity
DECIBEL(P2 [, P1])
P2is the numerator, supplied first.P1is the denominator. If omitted, it defaults to 1.- Both inputs must be numbers, and their quotient must be greater than zero.
The official DECIBEL entry gives the calculation explicitly:
=10*LOG10(P2/P1)
Here P2 and P1 are placeholders, not worksheet addresses to copy. The examples below supply actual cell references. For physical power comparisons, express both inputs in the same unit. NIST distinguishes the power-ratio expression 10*LOG10(P/P0) from the field-amplitude expression with a factor of 20. This function always uses the factor of 10, so do not apply it automatically to voltage or pressure ratios. NIST logarithmic quantities
Build a ratio worksheet
Create a worksheet named PowerRatios. Use A1:H7, with these headers in row 1:
Compared power | Reference power | Ratio | DECIBEL result | Formula check | Reversed ratio | Sum of directions | Reference note
Enter the following numeric inputs in A2:B7. The powers use the same arbitrary unit throughout. Column H can contain the description from the final column below.
| Row | A: Compared power | B: Reference power | H: Description |
|---|---|---|---|
| 2 | 1000 | 10 | Official example |
| 3 | 100 | 10 | Tenfold increase |
| 4 | 10 | 100 | Tenfold decrease |
| 5 | 50 | 50 | Equal powers |
| 6 | 20 | 10 | Twofold increase |
| 7 | 0.1 | 10 | One hundredth of reference |
Enter these formulas in row 2, then fill C2:G2 down through row 7:
C2: =A2/B2
D2: =DECIBEL(A2,B2)
E2: =10*LOG10(C2)
F2: =DECIBEL(B2,A2)
G2: =D2+F2
The independently calculated outputs are:
| Row | C: Ratio | D and E: dB | F: Reversed dB | G: Sum |
|---|---|---|---|---|
| 2 | 100 | 20 | -20 | 0 |
| 3 | 10 | 10 | -10 | 0 |
| 4 | 0.1 | -10 | 10 | 0 |
| 5 | 1 | 0 | 0 | 0 |
| 6 | 2 | 3.0102999566 | -3.0102999566 | 0 |
| 7 | 0.01 | -20 | 20 | 0 |
Noninteger outputs are rounded for display. The zero in G is the mathematical identity; a tiny numerical residual need not indicate a reversed-reference error. In contrast, a result with the wrong sign is a reason to check the order of the arguments.
Keep the worksheet intact. In J1:K4, add a separate default-reference comparison:
| Cell | Formula | Expected result |
|---|---|---|
| K2 | =DECIBEL(A2) |
30 |
| K3 | =DECIBEL(A2,1) |
30 |
| K4 | =DECIBEL(A2,B2) |
20 |
Use J2:J4 for labels. The first two formulas agree because the omitted denominator is 1, not the value in B2.
Follow two successive changes
On a separate worksheet named PowerChain, enter 100, 50 and 5 in A2:A4. Label A1 Power, B1 Stage change dB, and reserve D1:E5 for summaries.
B3: =DECIBEL(A3,A2)
B4: =DECIBEL(A4,A3)
E2: =B3+B4
E3: =DECIBEL(A4,A2)
E4: =10*LOG10((A3/A2)*(A4/A3))
E5: =DECIBEL(A4*1000,A2*1000)
B3 is approximately -3.0102999566 and B4 is -10. E2:E5 all give approximately -13.0102999566. The stage ratios multiply, while their decibel changes add. Multiplying both endpoint powers by the same positive unit-conversion factor leaves the ratio unchanged.
For a changed-input check, copy the entire sheet to ChangedEndpoint and replace A4 with 10. B3 stays approximately -3.0102999566; B4 becomes approximately -6.9897000434; E2:E5 become -10. Adding the raw powers would not produce either of these endpoint comparisons.
Excel export and practical limits
SoftMaker’s current reference warns that saving a workbook in Excel format replaces calculations using DECIBEL with their current fixed results. A retained displayed value is therefore not evidence that the formula will recalculate after an input changes. Keep a PlanMaker-format original when the live calculation matters.
For the positive numeric inputs in these examples, =10*LOG10(A2/B2) is the documented mathematical equivalent. Validate any replacement formula in the destination application before relying on an exported workbook.
A zero denominator is invalid, and a zero or negative quotient is outside the documented domain. The entry does not establish exact error tokens, text or blank coercion, or extreme-ratio precision. The power examples deliberately use positive numeric inputs; they do not certify other argument combinations or an export round trip.