Density Calculator
Density is mass packed into a given volume — the single number that tells you whether something floats or sinks in a given fluid, and a quick way to identify an unknown material.
Inputs
Result
2.5 g/cm³
2,500 kg/m³
How it works
ρ = m / V
How the density calculator works
ρ = m ÷ V, giving density in g/cm³ when mass is in grams and volume is in cm³ (equivalent to kg/L, and convertible to kg/m³ by multiplying by 1,000).
Worked example: 250 g object with 100 cm³ volume
- ρ = 250 ÷ 100 = 2.5 g/cm³.
- In kg/m³: 2.5 × 1,000 = 2,500 kg/m³ — denser than water (1,000 kg/m³), so this object would sink.
Common mistakes to avoid
Comparing densities in mismatched units
g/cm³ and kg/m³ differ by a factor of 1,000, not 1 — comparing a value in one unit directly against a reference value in the other without converting first leads to a factor-of-1000 error in judging the comparison.
Assuming density alone determines whether something floats
An object floats in a fluid if its overall density is less than the fluid's, but shape matters for how it floats (a steel ship floats despite steel being denser than water, because its overall shape displaces enough water to support its weight).
Frequently asked questions
Why is water's density used as a common reference point (1,000 kg/m³ or 1 g/cm³)?
It's a convenient, universally recognised benchmark — anything denser than water sinks in it, and anything less dense floats, making water density a natural comparison point for everyday materials.
Does density change with temperature?
Yes, generally — most materials expand slightly (becoming less dense) as they warm and contract (becoming denser) as they cool, though water has a well-known unusual exception around 4°C.
How is density used to identify an unknown material?
Every pure substance has a characteristic density under given conditions — measuring an unknown sample's mass and volume and comparing the resulting density to reference tables can help identify what it's made of.
What's the difference between density and specific gravity?
Specific gravity is a substance's density divided by water's density (a unitless ratio) — a specific gravity of 2.5 means 2.5 times denser than water, which is the same information as this calculator's g/cm³ result since water is defined as 1 g/cm³.
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