Pipe Insulation Thickness Calculator

Work out pipe insulation thickness instantly with clear inputs, formula shown and shareable results.

About Pipe Insulation Thickness Calculator

Heat flow through pipe insulation is a cylindrical conduction problem in series with an outside air film. The conduction resistance is ln(r2/r1) / (2 pi k) per foot and the film resistance is 1 / (h x 2 pi r2), so heat loss is the temperature difference divided by their sum. The same result gives the jacket surface temperature, which is the personnel-protection criterion.

Formulas

Cylindrical heat loss

q = ΔT / [ln(r2/r1) / (2 pi k) + 1 / (h x 2 pi r2)] per foot

Surface temperature

Ts = ambient + q x film resistance

Worked example

With the default values below, Pipe Insulation Thickness Calculator returns Heat loss with insulation of 17.42. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pipe outside diameterminimum 0.25 in: 2 in
Insulation thicknessminimum 0.25 in: 1.5 in
Fluid temperatureminimum -50 °F: 200 °F
Insulation conductivityminimum 0.01 BTU·in/h·ft²·°F: 0.25 BTU·in/h·ft²·°F

Results

Heat loss with insulation: 17.42 BTU/h per ft
Bare pipe heat loss: 112.31 BTU/h per ft
Insulation surface temperature: 78.1 °F
Heat loss reduction: 84.5% %

Step by step

1Values used
2Cylindrical heat loss
3Surface temperature
4Heat loss with insulation= 17.42 BTU/h per ft
5Bare pipe heat loss= 112.31 BTU/h per ft
6Insulation surface temperature= 78.1 °F
7Heat loss reduction= 84.5 %

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Verify insulation thickness against the applicable energy code tables and the manufacturer's tested conductivity at operating temperature.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Verify insulation thickness against the applicable energy code tables and the manufacturer's tested conductivity at operating temperature.

Frequently Asked Questions

How is the Pipe Insulation Thickness figure worked out?

q = ΔT / [ln(r2/r1) / (2 pi k) + 1 / (h x 2 pi r2)] per foot. Heat flow through pipe insulation is a cylindrical conduction problem in series with an outside air film.

Does more thickness always help?

Returns diminish quickly because resistance grows with the logarithm of the radius ratio. On small pipes there is also a critical radius below which added insulation increases loss by enlarging the outer surface.

What values do I need to enter?

This calculator takes 4 inputs: Pipe outside diameter, Insulation thickness, Fluid temperature, Insulation conductivity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.