Water Density Calculator
Calculate water density based on temperature, salinity, and pressure conditions
Calculate Water Density
Water temperature (0-100°C typical range)
Salt content in parts per thousand (0‰ = pure water)
External pressure (1 atm = sea level)
Water Density Results
Conditions: 20.0°C, 0‰ salinity, 1.00 atm
Pure water density: 998.29 kg/m³
Salt/pressure correction: +0.00 kg/m³
Will it Float or Sink?
Density Analysis
Example Calculation
Seawater at Room Temperature
Temperature: 20°C (room temperature)
Salinity: 35‰ (typical seawater)
Pressure: 1 atm (sea level)
Pure water density at 20°C: 998.2 kg/m³
Result
Salt water correction: +26.7 kg/m³
Final density: 1,024.9 kg/m³
This is why objects float more easily in seawater!
Factors Affecting Water Density
Temperature
Higher temperature = lower density
Maximum density at 4°C
Salinity
Higher salinity = higher density
Seawater ≈ 35‰ salinity
Pressure
Higher pressure = higher density
Minimal effect at surface levels
Common Water Types
Physics Tips
Water density = mass ÷ volume (ρ = m/V)
Objects float when their density < water density
Ice floats because it's less dense than liquid water
Thermal expansion decreases density with heat
Understanding Water Density
What is Water Density?
Water density is the mass of water per unit volume, typically expressed in kg/m³, g/mL, or lb/ft³. It represents how tightly water molecules are packed together under specific conditions of temperature, salinity, and pressure.
Why Does It Matter?
- •Determines buoyancy and whether objects float or sink
- •Affects ocean currents and water circulation
- •Important for engineering and fluid mechanics
- •Critical for marine biology and oceanography
Temperature Effects
Pure Water Density Formula (5th order polynomial):
ρ(T) = ρ₀ + a₁T - a₂T² + a₃T³ - a₄T⁴ + a₅T⁵
ρ₀ = 999.83311 kg/m³ (reference density)
T = Temperature in Celsius
Coefficients: Account for thermal expansion effects
Fun Fact: Water reaches maximum density at 4°C (39.2°F), which is why ice floats and lakes don't freeze solid from bottom up!
Salinity Effects
Salt water is denser than pure water because dissolved salts add mass without proportionally increasing volume. Salinity is measured in parts per thousand (‰) or practical salinity units (psu).
Typical Values:
• Pure water: 0‰
• Brackish water: 0.5-30‰
• Seawater: ~35‰
• Dead Sea: ~342‰
Pressure Effects
Water is slightly compressible, so higher pressure increases density. This effect is minimal at surface conditions but becomes significant at great ocean depths.
Pressure Examples:
• Sea level: 1 atm (101.325 kPa)
• 10m underwater: ~2 atm
• Deep ocean: 100+ atm
• Laboratory: Variable conditions