Convert British Thermal Units to Femtojoules
Convert British Thermal Units (BTU) to Femtojoules (fJ) instantly and accurately.
Conversion Formula
fJ = BTU × 1.055055853e+18
About British Thermal Units
A British Thermal Unit (BTU) - the heat to raise 1 lb of water by 1°F - equals exactly 1,055.05585262 J. It dominates US HVAC: room air conditioners are rated in BTU/h (5,000-24,000 BTU/h = 1.5-7.0 kW); one ton of refrigeration is exactly 12,000 BTU/h. Natural gas is billed in therms (100,000 BTU) in the US. Higher heating values: natural gas ~1,020-1,050 BTU/ft³; No. 2 fuel oil ~138,700 BTU/US gal; propane ~91,500 BTU/US gal. 1 BTU = 1,055.06 J = 252.164 cal = 0.29307 Wh.
About Femtojoules
A femtojoule (fJ) is 10⁻¹⁵ J - the scale of gamma-ray photons, molecular motor work, and state-of-the-art digital logic. The electron rest-mass energy is 81.87 fJ; a 100 keV X-ray photon carries 16.02 fJ. A single myosin II motor protein power stroke dissipates ~5-40 fJ. ATP hydrolysis under cellular conditions yields ~80-100 fJ of free energy. Advanced 3 nm CMOS gates switch at ~0.1-1 fJ per operation. Ultrafast fiber laser oscillators produce pulses of 0.1-10 fJ before amplification. 1 fJ = 10⁻¹⁵ J = 6.242 keV.
Quick Reference Table
| British Thermal Units (BTU) | Femtojoules (fJ) |
|---|---|
| 1 BTU | 1.055 × 1018 fJ |
| 2 BTU | 2.11 × 1018 fJ |
| 5 BTU | 5.275 × 1018 fJ |
| 10 BTU | 1.055 × 1019 fJ |
| 25 BTU | 2.638 × 1019 fJ |
| 50 BTU | 5.275 × 1019 fJ |
| 100 BTU | 1.055 × 1020 fJ |