Results

Results update automatically as you enter measurements.

Target thickness

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Projected panel mass

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Density ρ

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E_L

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E_C

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E_L / E_C

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G_LC

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Live: computed from current inputs

Panel measurements

Target main tap frequency (Hz)

Geometry

Mass & thickness

Modal taps

Target Panel Thickness Calculator

Use this tool to estimate the thickness for a top or back panel using its dimensions, mass, and tap-tone frequencies, so you can achieve consistent stiffness and a predictable acoustic response.

This calculator is based on the Gore & Gilet “Design” book (sections 4.5.2–4.5.3) and validated against their reference tables.

Overview & Required Measurements

Thickness isn’t the target, stiffness is. And one of the most straightforward ways to estimate stiffness in a guitar panel is by measuring its modal frequencies.

How to use this tool

Prepare the panel so it is smooth, rectangular, and evenly thicknessed.
Tap to identify the long grain, cross grain, and twisting modes.
Enter your measurements into the controls below.
Review the recommended target thickness.

Measurements required

Guitar box length & lower-bout width (mm)
Panel length, width, and thickness (mm)
Panel mass (g)
Tap-tone frequencies: long, cross, twist (Hz)
Target modal frequency for the finished top or back (Hz)

Accuracy & troubleshooting

Measure the fundamental of each mode (an FFT helps). Uneven thickness or coarse sanding can shift the tap frequencies; planing or scraping gives the most reliable readings.

If the recommended thickness seems unusually thin, re-measure your tap frequencies and compare them to the examples in the Gore & Gilet book. They should be in the same ballpark. If they’re not, send your numbers using the form below and we’ll take a look.

How the calculation works

This calculator is based on Gore & Gilet Vol. 1 (sections 4.5.2–4.5.3) and the example tables in the Design book. It converts your panel’s geometry, mass, and tap-tone frequencies into stiffness properties, then determines the thickness that corresponds to your target modal frequency.

Density (ρ)

Derived from the bare panel mass and dimensions.

ρ = mh · l · w

Young’s moduli (E_L, E_C)

Stiffness along and across the grain, calculated from density, geometry, and tap frequencies.

E = 0.94146 · ρ · l⁴ · f² h²

Shear modulus (G_LC)

Resistance to twisting, taken from the twisting mode.

G = 1.21585 · ρ · l² · w² · f² h²

Target thickness (h)

The thickness at which the panel will reach your chosen modal frequency.

h = 0.95977 · f · a² · √ρ √(E_L + (a/b)⁴ · E_C + (a/b)² · (0.02857 · E_L + 1.12 · G_LC))

URL tip: append ?long=80&cross=120&twisting=45 to prefill the modal taps when sharing results.

Need help with this tool? I read every message.

If your results don’t match what you’re expecting, share your measurements and a note. I’ll take a look.