Water Density vs Temperature Calculator
Find the density of pure, air free water at a given temperature, for DP level, flow and calibration calculations. The calculator uses the Kell equation, which matches standard tables closely.
- ρ(T) = (999.83952 + 16.945176T − 7.9870401×10⁻³T² − 46.170461×10⁻⁶T³ + 105.56302×10⁻⁹T⁴ − 280.54253×10⁻¹²T⁵) ÷ (1 + 16.879850×10⁻³T)
- ρ(20 °C) = 998.204 kg/m³
Water density by temperature
| °C | kg/m³ |
|---|---|
| 0 | 999.84 |
| 4 | 999.97 |
| 10 | 999.70 |
| 15 | 999.10 |
| 20 | 998.20 |
| 25 | 997.04 |
| 30 | 995.65 |
| 40 | 992.22 |
| 50 | 988.04 |
| 60 | 983.20 |
| 70 | 977.77 |
| 80 | 971.80 |
| 90 | 965.32 |
| 100 | 958.36 |
| 120 | 943.08 |
| 150 | 916.83 |
Kell Equation (1975)
T is the temperature in °C and ρ the density in kg/m³ at about 1 atm (saturation pressure above 100 °C). It applies to pure, air free water; dissolved salts or air change the density.
Worked example
Water at 20 °C has a density of 998.20 kg/m³; at 80 °C it is 971.8 kg/m³, about 2.6 % lighter.
Frequently Asked Questions
At what temperature is water densest?
At about 4 °C, where its density is 999.97 kg/m³.
Why does water density matter in instrumentation?
DP level, hydrostatic pressure and mass flow calculations all depend on density, which changes with temperature.
Does pressure change water density?
Only slightly: about 0.05 % per 10 bar. Temperature has a much larger effect.
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