Density Calculator
Calculate density, mass or volume — with material reference table and sink/float predictor
// Common Material Densities — Click to Load
Understanding Density
Density is the amount of mass packed into a given volume. It tells you how "heavy" a material is relative to its size. A golf ball and a ping-pong ball are similar in size but very different in mass — golf balls are denser.
Formulas
Archimedes and Floating
An object floats when its density is less than the density of the fluid it is placed in. Water has a density of 1.0 g/cm³. Any material with density below 1.0 g/cm³ will float in water; above 1.0 g/cm³ it will sink — assuming it is solid and fully submerged.
Density: The Property That Outed a Goldsmith
Built and verified by Andrius R. · Updated June 2026
Density — mass per unit volume, ρ = m ÷ V — is the original material fingerprint. It explains floating, identifies metals, and powered the most famous "Eureka!" in science. One formula, three rearrangements, and a reference table take you a long way.
The reference points that anchor everything
| Material | Density | Material | Density |
|---|---|---|---|
| Air (sea level) | ~1.2 | Aluminium | 2,700 |
| Wood (pine) | ~500 | Iron / steel | ~7,850 |
| Ice | 917 | Lead | 11,340 |
| Water | 1,000 | Gold | 19,300 |
Water's 1,000 kg/m³ (= 1 g/cm³ = 1 kg/L) is the universal yardstick — not a coincidence: the kilogram was originally defined from a liter of water. So a material's density in g/cm³ is its "times heavier than water" number: gold is 19.3× water.
Float or sink: one comparison
An object floats in a fluid if its average density is below the fluid's. Ice at 917 floats with ~92% submerged — the iceberg ratio — because water is the rare substance that expands on freezing (which is also why pipes burst and why lakes freeze top-down, letting fish overwinter beneath). Steel at 7,850 sinks as a lump but floats as a ship: the hull's shape encloses air, dragging the average density of "steel + enclosed air" below 1,000. Same trick in reverse for submarines (flood tanks to sink, blow them to rise) and hot-air balloons (heated air at ~0.9 kg/m³ floats in cooler 1.2 air).
Archimedes and the crown
The classic story: King Hiero suspected his goldsmith had cut the crown's gold with silver; Archimedes (legend says, mid-bath) realized submersion reveals volume. The numbers show how decisive it is: a 1 kg crown of pure gold displaces 1,000 ÷ 19.3 ≈ 51.8 cm³ of water; the same mass in silver (10,490 kg/m³) displaces 95.3 cm³ — nearly double. Any silver in the alloy shifts the displacement measurably. Density-as-fingerprint still works exactly this way: weigh an object, measure its water displacement, divide, and check the table — a "gold" bar reading 8.9 g/cm³ is gold-plated copper, no lab required. (Modern fakes use tungsten — 19,250 kg/m³, within 0.3% of gold — which is why serious assays add ultrasound to the density test.)
Density's quieter day jobs
- Weather and ocean currents: warm air rises because it's less dense; cold dense air sinks. The same density-driven convection stirs oceans, boils your pasta water and once kept lava lamps in business.
- Layered drinks and oil spills: liquids stack by density — honey under water under oil under spirits. Oil's ~900 kg/m³ is why spills float and spread rather than sinking away.
- "Heavier than it looks": our brains estimate weight from size assuming familiar densities — why a lead fishing weight or a gold ring surprises the hand, and why airlines weigh bags instead of eyeballing them.
- Quality control: from battery acid (hydrometers read charge via density) to milk, brewing wort and antifreeze mixtures — measuring density is often the cheapest possible chemistry test.
// Float Test
Anything with density less than 1 g/cm³ floats in water. Ice (0.917 g/cm³) floats — that's why icebergs show only ~10% above the surface.
// Densest Element
Osmium is the densest known element at ~22.59 g/cm³ — more than twice as dense as lead (11.34 g/cm³).
// Human Body
The average density of the human body is ~985 kg/m³ — just slightly less than water, which is why we barely float.
// Cooking
Oil floats on water because it's less dense (~0.92 g/cm³). This is why oil and water don't mix — they separate by density.