Calculate water density at any temperature (0–100°C), salinity, and pressure. Includes anomalous expansion, viscosity, speed of sound, and density vs temperature table.
The Water Density Calculator computes the precise density of water at any temperature from 0°C to 100°C, with corrections for salinity and pressure. Water\'s density is perhaps the most important physical constant in science and engineering — it defines the liter, underpins buoyancy calculations, and serves as the reference standard for specific gravity measurements.
Water exhibits anomalous density behavior: unlike almost every other substance, it reaches maximum density not at its freezing point but at approximately 3.98°C (999.97 kg/m³). Below this temperature, water expands as it cools further, which is why ice floats and lakes freeze from the top down — a property essential to aquatic life. This calculator uses the Tanaka et al. (2001) recommended formula derived from IAPWS-95 data for high-accuracy freshwater density.
Beyond basic density, the tool provides dynamic viscosity, specific heat, thermal expansion coefficient, and speed of sound — all temperature-dependent properties needed for fluid dynamics, heat transfer, and acoustics calculations. The salinity correction handles seawater and brine solutions, while the pressure correction extends results to elevated pressures.
Accurate water density values are essential throughout science and engineering. Hydrologists model lake stratification, brewers calculate specific gravity, marine engineers design submersibles, HVAC engineers size water systems, and calibration laboratories reference water density to verify volumetric glassware. Rather than interpolating printed steam tables, this calculator gives instant, accurate density plus viscosity and other properties at any conditions.
The anomalous expansion visualization is also a valuable teaching tool for physics and chemistry courses.
Density (Tanaka 2001): ρ(T) = 999.97495 × (1 − ((T − 3.983035)² × (T + 301.797)) / (522528.9 × (T + 69.34881))) where T is temperature in °C. Salinity correction: Δρ ≈ 0.7 × S (kg/m³ per g/L of dissolved salt). Pressure correction: Δρ ≈ 0.046 × (P − 1) kg/m³ per atm above atmospheric. Specific volume: v = 1/ρ. Thermal expansion coefficient: β = −(1/ρ)(dρ/dT).
Result: ρ = 998.204 kg/m³, μ = 1.002 mPa·s, cₚ = 4,183 J/(kg·K)
At 20°C and 1 atm, freshwater has a density of 998.2 kg/m³ — slightly less than its maximum at 4°C. The dynamic viscosity of 1.002 mPa·s (centipoise) is the standard reference for fluid dynamics. One liter weighs 998.2 grams.
Water is one of very few substances that expand upon freezing. This anomaly arises from hydrogen bonding: as water cools below 4°C, molecules begin arranging themselves into the hexagonal (ice-like) lattice that is less dense than the disordered liquid. At 0°C, the density drops to 999.84 kg/m³, and upon freezing drops sharply to 917 kg/m³. This 8.3% expansion exerts tremendous pressure — enough to burst pipes and split rocks — and is a major agent of weathering.
In the ocean, density depends on temperature, salinity, and pressure. Cold, salty water is denser and sinks, driving the global thermohaline circulation that distributes heat across the planet. Oceanographers measure density with CTD instruments (Conductivity, Temperature, Depth) and compute density from the UNESCO equation of state. Even tiny density differences (0.01 kg/m³) drive massive water flows across ocean basins.
Water density appears in countless engineering calculations: calibrating volumetric glassware, computing hydrostatic pressure in tanks and dams, sizing pumps and heat exchangers, determining specific gravity of liquids and solids, and verifying the purity of pharmaceutical-grade water. In brew|distillation industries, precise density measurements reveal sugar and alcohol content through specific gravity or Plato/Brix scales — all referenced to water\'s density.
Below 4°C, hydrogen bonding forces water molecules into an increasingly open hexagonal structure (pre-ice lattice), causing expansion. This anomalous behavior is unique to water and a few other substances.
Dissolved salts increase density by about 0.7–0.8 kg/m³ per g/L. Standard seawater (35 g/L) has a density of about 1,025 kg/m³. The Dead Sea (~340 g/L) reaches 1,240 kg/m³.
No. At 4°C it\'s 999.97 kg/m³ — very close to 1,000 but not exact. At 20°C it\'s about 998.2 kg/m³. The original kilogram definition targeted 1 dm³ of water at maximum density.
Water is nearly incompressible. At 100 atm (depth of ~1,000 m), density increases by only 0.5%. The correction is about 0.046 kg/m³ per atmosphere above 1 atm.
Ice at 0°C has a density of 917 kg/m³, about 8.3% less than liquid water at 0°C (999.8 kg/m³). The crystalline hydrogen-bond network in ice creates an open structure with lower density.
About 1,482 m/s at 20°C — roughly 4.3 times faster than in air. It increases with temperature up to about 74°C, then decreases. This is critical for sonar and underwater acoustics.