Specific heat capacity of liquid water
| Value | 4181.6 J/(kg·K) |
| Status | Conventional / typical value |
| Source | IAPWS-95; NIST Chemistry WebBook |
| Categories | ThermodynamicMaterial Properties |
| joule per kilogram-kelvin | 4,181.6 J/(kg·K) |
| kilojoule per kilogram-kelvin | 4.1816 kJ/(kg·K) |
| calorie per gram-Celsius | 0.99942639 cal/(g·°C) |
| BTU per pound-Fahrenheit | 0.998758 BTU/(lb·°F) |
Learning zone
Water's specific heat is extraordinary: raising one kilogram by one kelvin costs about 4182 joules, four times the figure for air and nine times that for copper. Hydrogen bonding is responsible — much of the added energy goes into breaking and reforming the bond network rather than into faster motion. That anomaly is why oceans buffer the climate, why a coolant loop the size of a garden hose can carry a megawatt, and why the hydronic rule of thumb 500 × gpm × ΔT gives BTU/h.
It varies less than you would expect, dipping to a shallow minimum of 4178 J/(kg·K) near 35 °C and rising to 4216 at 100 °C, so a single value is usually good to half a percent across the useful range. The historical calorie was defined to make this number exactly 4184 J/(kg·K) — one calorie per gram per degree — which is why 4184 and 4186 both circulate: they correspond to water at 20 °C and at 15 °C respectively.