Convert BTU·in/(h·ft²·°F) to cal/(s·cm·°C)

Formula

cal/(s·cm·°C) = BTU·in/(h·ft²·°F) × 0.0003447129274959

or cal/(s·cm·°C) = BTU·in/(h·ft²·°F) ÷ 2900.964600499

Derivation from SI units:

• 1 BTU_IT·in/(h·ft²·°F) = 1055.05585262 J × 0.0254 m ÷ (3600 s × 0.09290304 m² × 5/9 K) = 0.1442278889 W/(m·K) (exact)
• 1 cal_th/(s·cm·°C) = 4.184 J ÷ (1 s × 0.01 m × 1 K) = 418.4 W/(m·K) (exact)
• 1 BTU·in/(h·ft²·°F) = 0.1442278888643 W/(m·K) ÷ 418.4 W/(m·K) per cal/(s·cm·°C) = 0.0003447129274959 cal/(s·cm·°C)

Both units are defined exactly, so the factor is exact. BTU·in/(h·ft²·°F) definition: BTU inch per hour square foot degree Fahrenheit; cal/(s·cm·°C) definition: calorie per second centimetre degree Celsius.

Worked examples

1. A reading of 0.22 BTU·in/(h·ft²·°F) converts to 0.00007583684405 cal/(s·cm·°C).
   0.22 BTU·in/(h·ft²·°F) × 0.0003447129275 = 0.00007583684405 cal/(s·cm·°C)
2. A value of 0.3 BTU·in/(h·ft²·°F) is 0.0001034138782 cal/(s·cm·°C).
   0.3 BTU·in/(h·ft²·°F) × 0.0003447129275 = 0.0001034138782 cal/(s·cm·°C)

Where it's used

BTU·in/(h·ft²·°F) are used for US insulation k-values (ASTM C177, C518), while calories per second centimetre degree Celsius appear in older scientific literature. Both measure thermal conductivity (k, λ), so the conversion is a fixed factor.

BTU·in/(h·ft²·°F) to other thermal conductivity units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "British thermal unit_IT inch per hour square foot degree Fahrenheit [Btu_IT · in/(h · ft² · °F)]".
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "calorie_th per centimeter second degree Celsius [cal_th/(cm · s · °C)]".

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.