What Is the Density of Water at Different Temperatures? A Complete Table
Water reaches its maximum density at 4°C (39.2°F), where one liter weighs 1.000 kilograms. As temperature moves away from that point, water expands and becomes less dense. The density of water at different temperatures follows a predictable pattern: it decreases as water heats up, and it also decreases when water cools below 4°C toward freezing. This behavior is unusual compared to most liquids, which get denser as they cool all the way to their freezing point.
Why Water Density Changes with Temperature
Water molecules are polar, meaning they have a slight positive charge on one side and a slight negative charge on the other. This polarity causes molecules to form hydrogen bonds with each other. At higher temperatures, molecules move faster and push apart, reducing density. At lower temperatures, they slow down and pack more tightly.
The exception occurs between 0°C and 4°C. In this range, water molecules arrange into a more open hexagonal structure as they approach freezing. This structure takes up more space than the same number of molecules in a liquid state, so the density drops. Ice at 0°C is about 9% less dense than liquid water at 0°C, which is why ice floats.
Density Values for Common Temperatures
The table below shows the density of pure water at standard atmospheric pressure for temperatures from 0°C to 100°C. These values come from standard reference data published by the National Institute of Standards and Technology and the Engineering ToolBox.
| Temperature (°C) | Density (kg/m³) | Density (g/mL) |
|---|---|---|
| 0 (ice) | 916.7 | 0.917 |
| 0 (liquid) | 999.8 | 0.9998 |
| 4 | 1000.0 | 1.0000 |
| 10 | 999.7 | 0.9997 |
| 20 | 998.2 | 0.9982 |
| 25 | 997.0 | 0.9970 |
| 30 | 995.7 | 0.9957 |
| 40 | 992.2 | 0.9922 |
| 50 | 988.0 | 0.9880 |
| 60 | 983.2 | 0.9832 |
| 70 | 977.8 | 0.9778 |
| 80 | 971.8 | 0.9718 |
| 90 | 965.3 | 0.9653 |
| 100 | 958.4 | 0.9584 |
At 4°C, density reaches exactly 1000 kg/m³ by definition. At 20°C, a common room temperature, water density is about 998.2 kg/m³. At boiling point (100°C), it drops to 958.4 kg/m³, a decrease of roughly 4%.
How to Use These Values in Calculations
If you need to convert between volume and mass for water at a given temperature, multiply the volume (in liters) by the density (in g/mL) to get mass (in kilograms). For example, 5 liters of water at 25°C has a mass of 5 × 0.9970 = 4.985 kg. At 60°C, the same volume weighs 5 × 0.9832 = 4.916 kg.
Factors That Influence Water Density Beyond Temperature
Temperature is the main factor, but other variables also affect water density.
Dissolved Substances
Salt and other dissolved solids increase water density. Seawater has a higher density than pure water, which is why ships float higher in salt water than in fresh water. The effect is proportional to the concentration of dissolved solids.
Pressure
Pressure compresses water slightly, increasing its density. In the deep ocean, pressure can increase density by a few percent. For most surface-level applications, pressure effects are negligible. The standard density values in the table above assume atmospheric pressure.
Practical Applications of Water Density Knowledge
Engineering and Industry
Engineers use water density to design cooling systems, pipelines, and water treatment plants. Density changes affect pump sizing, flow rates, and heat transfer calculations. A hot water heating system must account for the lower density of hot water to ensure proper circulation.
Cooking and Food Science
Recipes that measure ingredients by volume can be affected by water temperature. A cup of boiling water weighs less than a cup of cold water because the density is lower. For precise baking, weighing ingredients is more reliable than using volume measures.
Environmental Science
Lake stratification and ocean currents depend on density differences driven by temperature and salinity. Understanding these patterns helps scientists predict weather, track pollution, and manage fisheries.
Key Takeaways
- Water reaches its maximum density of 1000 kg/m³ at 4°C.
- Density decreases as water warms above 4°C and as it cools toward freezing.
- Ice is less dense than liquid water, which is why ice floats.
- The density of water at different temperatures follows a predictable, well-documented pattern useful in science, engineering, and everyday life.
- Dissolved substances and pressure also affect water density, but temperature has the largest practical influence.
