Formula & worked example
Q=U·π·D·L·ΔT.
A 50 mm OD, 20 m pipe at U=3 W/m²K and 50 K difference loses about 471 W.
Heating & HVAC engineering calculator · Updated Sep 17, 2026
Pipe Heat Loss Calculator — U-Value, Diameter, Length & Temperature
Estimate steady pipe heat loss from overall U-value, outside diameter, length and fluid-to-ambient temperature difference.
Inputs
Live result
Outside surface area 3.1415927 m²
Temperature difference 50 K
Heat loss 471.2389 W (1,607.9339 BTU/h)
Heat loss per metre 23.561945 W/m
Assumptions & limits
- Entered U-value must represent the intended pipe/insulation/film system.
- Fittings, supports, valves and changing fluid temperature are not automatically added.
Frequently asked questions
What does this Pipe Heat Loss Calculator calculate?
Estimate steady pipe heat loss from overall U-value, outside diameter, length and fluid-to-ambient temperature difference.
What units are supported?
Inputs state their unit basis and results include practical SI and US customary equivalents where useful, so the calculation can be checked against field data and equipment schedules.
Can I use this for final equipment selection?
Use it for transparent first-pass sizing and engineering cross-checks. Final selections should use measured conditions, manufacturer performance data and applicable codes or design standards.