密度计算器
使用公式 ρ = m/V 计算密度(ρ)、质量(m)或体积(V)。输入任意两个值即可找到第三个值，支持各种单位和常见材料。
Enter Calculation Parameters
Input Parameters
About Density Calculation
What is Density?
Density is a physical property of matter defined as mass per unit volume. The symbol for density is ρ (Greek letter rho), and it's formula is ρ = m/V, where m is mass and V is volume.
Density is an intensive property, which means its value doesn't depend on the amount of material present. A small sample of lead has the same density as a large sample of lead. This makes density useful for identifying substances and understanding their behavior.
Examples of densities include water (1000 kg/m³), air (1.225 kg/m³), iron (7870 kg/m³), and gold (19300 kg/m³). Materials with densities less than that of water (1000 kg/m³) will float in water, while those with higher densities will sink.
What is Density?
Density is a physical property of matter defined as mass per unit volume. The symbol for density is ρ (Greek letter rho), and it's formula is ρ = m/V, where m is mass and V is volume.
Density is an intensive property, which means its value doesn't depend on the amount of material present. A small sample of lead has the same density as a large sample of lead. This makes density useful for identifying substances and understanding their behavior.
Examples of densities include water (1000 kg/m³), air (1.225 kg/m³), iron (7870 kg/m³), and gold (19300 kg/m³). Materials with densities less than that of water (1000 kg/m³) will float in water, while those with higher densities will sink.
How to Use the Density Calculator
This calculator allows you to determine any one of the three variables in the density equation (ρ = m/V) when you know the other two. Here's how to use it:
- Select your calculation mode: Calculate Density, Calculate Mass, or Calculate Volume.
- Enter the two known values in their respective fields.
- Select the appropriate units for each value. The calculator supports a wide range of units.
- For mass or volume calculations, you can select a common material from the dropdown to automatically use its density.
- Click the Calculate button to see the results.
Tip: Pay attention to the units you're working with. The calculator will handle conversions, but understanding the units helps interpret the results correctly.
Density Calculation Formulas
The density of an object or substance is determined by its mass and volume. The following formulas show how to calculate density, mass, or volume when the other two values are known:
Density Formula (ρ = m/V)
When the mass (m) and volume (V) are known, density (ρ) can be calculated by dividing the mass by the volume. The standard unit for density is kilogram per cubic meter (kg/m³) in the SI system.
Mass Formula (m = ρ × V)
When the density (ρ) and volume (V) are known, mass (m) can be calculated by multiplying the density by the volume. Mass is typically measured in kilograms (kg) in the SI system.
Volume Formula (V = m/ρ)
When the mass (m) and density (ρ) are known, volume (V) can be calculated by dividing the mass by the density. Volume is typically measured in cubic meters (m³) in the SI system.
Relative Density Formula
Relative density (or specific gravity) is the ratio of the density of a substance to the density of a reference substance, usually water at 4°C (1000 kg/m³). It's a dimensionless quantity with no units.
Unit Conversion Reference
Use these conversion factors when working with different units:
Mass Units:
- 1 kg = 1000 g
- 1 kg = 2.20462 lb
- 1 ton = 1000 kg
- 1 lb = 16 oz
Volume Units:
- 1 m³ = 1000 L
- 1 m³ = 1,000,000 cm³
- 1 m³ = 35.3147 ft³
- 1 ft³ = 1728 in³
- 1 gal = 3.78541 L
Density Units:
- 1 g/cm³ = 1000 kg/m³
- 1 kg/L = 1000 kg/m³
- 1 lb/ft³ = 16.0185 kg/m³
Applications of Density
Density is an important property with many practical applications across various fields:
Scientific Research
Density is used to identify substances, study phase changes, understand fluid behavior, and analyze material properties. It's a fundamental concept in chemistry, physics, and materials science.
Engineering and Construction
Engineers use density in designing structures, selecting materials, calculating buoyancy forces, and determining weight distribution. Knowledge of material density is crucial for ensuring structural integrity and performance.
Medical Applications
In medicine, density measurements help assess bone health (bone mineral density), evaluate body composition, and analyze blood samples. Variations in tissue density can indicate different health conditions.
Geology and Earth Sciences
Geologists use density to identify minerals, study Earth's structure, analyze soil composition, and understand tectonic processes. Different rock types have characteristic densities.
Everyday Applications
Density affects many everyday phenomena, from why some objects float and others sink, to how hot air balloons work, to why oil and water separate. Understanding density helps explain numerous practical observations.
Common Material Densities
| Material | Density (kg/m³) | Relative Density |
|---|---|---|
| Water | 1000 kg/m³ | 1.0 |
| Ice | 917 kg/m³ | 0.917 |
| Aluminum | 2700 kg/m³ | 2.7 |
| Iron | 7870 kg/m³ | 7.87 |
| Gold | 19300 kg/m³ | 19.3 |
Frequently Asked Questions
Why is water often used as a reference for relative density?
Water is used as a reference because it's abundant, well-characterized, and has a convenient density of 1000 kg/m³ (or 1 g/cm³) at 4°C. This makes relative density calculations straightforward - materials with relative density less than 1 float in water, while those greater than 1 sink.
How does temperature affect density?
Most materials expand when heated and contract when cooled, changing their volume while mass remains constant. Since density is mass divided by volume, most substances become less dense as temperature increases. Water is a notable exception between 0-4°C, where it actually becomes more dense as it warms before following the normal pattern above 4°C.
What's the difference between density and weight?
Density is mass per unit volume (ρ = m/V), while weight is the force exerted on an object due to gravity (W = mg, where g is gravitational acceleration). Density is an intrinsic property that doesn't change with location, whereas weight varies depending on the strength of the gravitational field.
Can density be negative?
No, density cannot be negative because both mass and volume are always positive quantities. However, in some specialized contexts like quantum physics or certain engineered materials (metamaterials), effective or apparent "negative density" concepts may be discussed.
What material has the highest density?
Osmium is the densest naturally occurring stable element, with a density of approximately 22,590 kg/m³. Some synthetic elements and neutron star material have even higher densities, but aren't encountered in everyday circumstances.