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Pipe Insulation Surface-Temperature Calculator

Estimate insulated-pipe outer-surface temperature and heat transfer per unit length with cylindrical conduction and outside convection.

Why it matters: Surface temperature affects personnel protection, condensation risk, and energy loss or gain.

User inputs

Enter field measurements

7 inputs
Select I-P or SI units. Unit-dependent entries are converted when the selection changes.
°F or °CAssumed temperature at the insulation inner surface.
°F or °CRepresentative ambient dry-bulb temperature.
in. or mmActual outside diameter at the insulation inner surface.
in. or mmRadial insulation thickness.
Btu/(h·ft·°F) or W/(m·K)Representative conductivity at the mean insulation temperature.
Btu/(h·ft²·°F) or W/(m²·K)Entered combined outside heat-transfer coefficient; radiation treatment must be consistent with this value.

Calculated result

Engineering evaluation

Steady-state estimate complete
Estimated insulation surface temperature (Ts)74.92 °F
Heat transfer per unit length (qL)
-10.98 Btu/(h·ft)
Cylindrical conduction resistance (Rcond)
2.997 h·ft·°F/Btu
Outside convection resistance (Rconv)
0.463 h·ft·°F/Btu

Engineering interpretation

The entered steady-state model estimates an outer surface temperature of 74.92 °F and heat transfer -10.98 Btu/(h·ft).

Important limitations

  • This simplified model assumes the pipe or fluid temperature at the insulation inner surface and a uniform entered outside coefficient. Vapor barriers, joints, supports, radiation, wind, moisture, emissivity, thermal bridges, and manufacturer conductivity data require separate review.

Engineering knowledge center

Understand the calculation—not just the answer

2026-08-07 · Free Library
Governing relationships
r1 = D1/2
r2 = r1+t
Rcond = ln(r2/r1)/(2πk)
Rconv = 1/(ho·2πr2)
qL = (Tf−Ta)/(Rcond+Rconv)
Ts = Ta+qL·Rconv
Current substitution

Rcond = 2.997; Rconv = 0.463; qL = (42−80)/(2.997+0.463) = -10.98; Ts = 80+-10.98×0.463 = 74.92 °F.

Calculation sequence

Step-by-step method

  1. Convert pipe radius and insulation thickness to feet or metres.
  2. Calculate cylindrical conduction and outside-film resistances per unit length.
  3. Calculate heat transfer and the outside surface temperature.

Equation legend

Inputs and calculated quantities

Tf
Fluid or pipe temperature — °F or °C
Ta
Ambient air temperature — °F or °C
D1
Pipe outside diameter — in. or mm
t
Insulation thickness — in. or mm
k
Insulation conductivity — Btu/(h·ft·°F) or W/(m·K)
ho
Outside film coefficient — Btu/(h·ft²·°F) or W/(m²·K)
Ts
Estimated insulation surface temperature — °F
qL
Heat transfer per unit length — Btu/(h·ft)
Rcond
Cylindrical conduction resistance — h·ft·°F/Btu
Rconv
Outside convection resistance — h·ft·°F/Btu

Continue the evaluation

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Engineering calculation disclaimer

These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.

Read the full use and limitation statement