Water Density Specific Weight

Overview

Density is the ratio of mass to volume:

$\rho = \frac{m}{V}$

where $\rho$ is density, $m$ is mass and $V$ is volume. Density is commonly expressed as g/cm^3, kg/m^3, lb/ft^3 or sl/ft^3.

Pure water reaches its maximum density, approximately 1000 kg/m^3 or 1.940 slug/ft^3, at 4 degC (39.2 degF). Above this temperature the density decreases as water expands.

Specific weight is the ratio of weight to volume:

$\gamma = \frac{m g}{V} = \rho g$

where $\gamma$ is specific weight and $g$ is the acceleration of gravity. Standard gravity is normally taken as 9.80665 m/s^2 or 32.17405 ft/s^2.

For water at 4 degC in SI units:

$\gamma = 1000 \; \text{kg/m}^3 \times 9.807 \; \text{m/s}^2 = 9807 \; \text{N/m}^3 = 9.807 \; \text{kN/m}^3$

In Imperial engineering units, water density at 39 degF is about 1.940 sl/ft^3:

$\gamma = 1.940 \; \text{sl/ft}^3 \times 32.174 \; \text{ft/s}^2 = 62.4 \; \text{lbf/ft}^3$

Online Water Density Calculator

The original page includes a calculator for liquid water density at a given temperature and reports density as g/cm^3, kg/m^3, lb/ft^3, lb/gal(US liq) and sl/ft^3. The original valid temperature ranges are 0-370 degC, 32-700 degF, 273-645 K and 492-1160 degR.

The calculator below uses a standard atmospheric-pressure approximation for liquid water near the ordinary liquid range. Use the tabulated values for design work, saturation conditions above 100 degC, or elevated pressure.

Variables

Interactive Density Charts

The original page contains three density images: water density versus temperature in degC, water density versus temperature in degF, and density versus temperature at elevated pressure. The charts below recreate those image datasets from the original tabulated values so the curves can be inspected interactively.

Density, Specific Weight and Thermal Expansion in degC

Values from 0-100 degC are at 1 atm. Values above 100 degC are at saturation pressure.

Density, Specific Weight and Thermal Expansion in degF

Values from 32-212 degF are at 1 atm. Values above 212 degF are at saturation pressure.

Density and Specific Weight at 1000 psi

The original table gives water density and specific weight at 1000 psi (68.1 atm). At this pressure, the boiling point noted in the source is 284.8 degC (544.58 degF).

Density and Specific Weight at 10000 psi

Unit Conversions and Examples

Weight per U.S. gallon is based on 7.48 gal/ft^3.

One U.S. liquid gallon equals:

• 3.7854 l
• 0.8327 gal(UK)
• 0.8594 gal(US dry)
• 0.1074 bu(US dry)
• 0.4297 pk(US dry)
• 4 qt(US liq)
• 8 pt(US liq)
• 16 c(US)
• 32 gi(US liq)
• 128 fl oz(US)
• 1024 fl dr(US)
• 3.7854e-3 m^3
• 0.1337 ft^3
• 4.951e-3 yd^3

Density conversion from 1 kg/m^3:

Example 2 from the original page converts the density of water at 20 degC:

$998.21 \; \text{kg/m}^3 \times 0.0005780 = 0.5797 \; \text{oz/in}^3$

Example 3 calculates the mass of water in a tank. A tank with volume 10 m^3 contains hot water at 190 degF. From the degF table, the density is 966.8 kg/m^3:

$10 \; \text{m}^3 \times 966.8 \; \text{kg/m}^3 = 9668 \; \text{kg}$

Original Source Images

The following original source images are preserved to avoid losing visual reference material. When an image contains chart or tabular data, its extracted values are represented in the page tables, calculators, or interactive charts; remaining images are retained as visual source references.

Engineering Notes

• The density-temperature relationship is not linear. The volumetric expansion coefficient is therefore not constant across the temperature range.
• Water is densest near 4 degC. This anomaly matters in hydrostatics, natural convection, freeze protection and storage-tank calculations.
• Above the normal boiling point, the 1-atm tables are no longer liquid-water data at atmospheric pressure; the original source reports values at saturation pressure.
• Pressure increases liquid-water density. The pressure chart and high-pressure tables show the difference between 1 atm or saturation, 1000 psi and 10000 psi.
• In U.S. customary tables, lbm/ft^3 and lbf/ft^3 are numerically similar at standard gravity, but density and specific weight are different physical quantities.

References

• Engineering ToolBox - Water Density, Specific Weight and Thermal Expansion Coefficients
• Original image datasets restored as interactive charts from water_density_C.jpg, water_density_F.jpg and Water_density_temp_pressure_F.jpg.