Density Calculator
Compute density (ρ), mass, or volume
How to Use
- Select which variable you want to calculate (density, mass, or volume)
- Enter the two known values with their respective units
- Choose your preferred units for input and output
- Click calculate to see the result with automatic unit conversions
- Review the detailed calculation breakdown
What is Density?
Density is a fundamental physical property that describes how much mass is contained in a given volume. It's commonly expressed as mass per unit volume and is an important concept in physics, chemistry, engineering, and everyday life.
Density helps us understand why some objects float while others sink, why hot air rises, and how materials behave under different conditions. It's essential for everything from designing ships to understanding atmospheric phenomena.
Density Formula
The basic density formula is:
ρ = m / V
Where:
- ρ (rho) = density
- m = mass
- V = volume
This formula can be rearranged to solve for any variable:
- Mass: m = ρ × V
- Volume: V = m / ρ
Common Density Units
Density can be expressed in various units depending on the application:
| Unit | System | Common Use |
|---|---|---|
| kg/m³ | SI | Scientific calculations, engineering |
| g/cm³ | CGS | Chemistry, materials science |
| g/mL | Laboratory | Liquids in lab settings |
| lb/ft³ | Imperial | US construction, materials |
| lb/in³ | Imperial | Dense materials, metals |
Water has a density of approximately 1,000 kg/m³ or 1 g/cm³ at 4°C, which serves as a reference point for many calculations.
Real-World Examples
Understanding density helps explain everyday phenomena:
- Ice floats on water because it's less dense (about 917 kg/m³) than liquid water (1,000 kg/m³)
- Helium balloons rise because helium is much less dense than air
- Oil floats on water due to lower density (about 800-900 kg/m³)
- Metals sink in water because they're much denser (iron: 7,874 kg/m³)
Factors Affecting Density
Several factors can affect the density of materials:
- Temperature: Most materials expand when heated, decreasing density
- Pressure: Increasing pressure typically increases density
- Composition: Different materials have different inherent densities
- State of matter: Solids are generally denser than liquids, which are denser than gases
Frequently Asked Questions
- Why is water's density exactly 1 g/cm³?
- Water's density was historically used to define the gram. By definition, 1 gram is the mass of 1 cubic centimeter of water at 4°C (its temperature of maximum density).
- How do I calculate the density of an irregular object?
- For irregular objects, measure the mass directly, then find volume using water displacement (Archimedes' principle). Submerge the object in water and measure the volume of water displaced.
- Why do ships float if they're made of steel?
- Ships float because of their overall density. While steel is dense, ships have large volumes filled with air. The average density (total mass ÷ total volume) is less than water's density, so they float.
- What's the difference between density and specific gravity?
- Specific gravity is the ratio of a substance's density to the density of water. It's dimensionless, while density has units. Specific gravity of 1.0 means the substance has the same density as water.
- How does temperature affect density calculations?
- Temperature affects both mass and volume. Most materials expand when heated, increasing volume and decreasing density. For precise calculations, specify the temperature or use temperature-corrected values.
- Can density be negative?
- No, density cannot be negative. Both mass and volume are always positive quantities, so their ratio (density) must also be positive.