Density Calculator
How hard a substance crowds its space: ρ = m/V — the scam test, the float test, and the answer to what any tank or drum of the stuff would weigh.
Density Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Pure, homogeneous samples — no mixtures or porosity corrections
- Temperature noted by the user, not modelled
In short: A 1.2 kg sample filling 0.001 m³ (one litre) has ρ = 1,200 kg/m³ — specific gravity 1.200000, twenty percent denser than fresh water, so it sinks. The comparison card carries the classics: water 1,000, sea ice about 917 (which is WHY it floats — water is the rare substance that expands when it freezes), gold 19,300 (the panner's scam test: fool's gold at about 5,000 never fooled the hand that hefted both), air 1.225 at sea level. The volume card prices any container: a 200-litre drum of this sample would weigh 240 kg — mass per cubic metre, scaled to your tank.
Formula
ρ = m/V · specific gravity = ρ/1,000 · floats iff ρ < fluid · m = ρ·V for any volume
Density is crowding: mass per cubic metre, a property of the SUBSTANCE rather than the sample. Specific gravity is the same number divided by water's 1,000 — dimensionless, so it compares against the fluid every practical question already cares about. The float test falls out: less crowded than the fluid, it floats.
Worked Example
- Weigh the sample, measure its volume (1 L = 0.001 m³).
- Read ρ and its specific gravity against water.
- Read the float verdict — the comparison that settles the sink-or-swim argument.
- Use the volume card to price any drum or tank of the substance.
Defaults: 1,200 kg/m³, SG 1.200000 — sinks. A 0.9 kg litre (900) floats: oil on water. 19.3 kg per litre is gold's signature; 5,000-ish is the fool's.
Strengths & Limits Of This Model
Where this engine is strong
- Float verdict and specific gravity from one divide
- Any-volume pricing for tanks and drums
Where it stops
- No thermal expansion terms
- No mixture or blend densities
Practical Use Cases
Assaying
the heft test, made arithmetic
Kitchens & brewing
syrups and worts by gravity
Teaching
one number that explains floating
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Density Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why is water the comparison?
Because it is the fluid every practical question already lives in: boats, pipes, baths, rain. Specific gravity — density divided by 1,000 — turns the comparison into a dimensionless verdict: above 1 sinks in fresh water, below 1 floats, and seawater's higher number moves the bar a little.
Why does ice float when nothing else solid does?
Because water is the anomaly: it EXPANDS as it freezes, dropping to about 917 kg/m³ — which is why ponds freeze from the top and life continues below. Nearly every other substance sinks into its own melt; the page's water card prices the exception.
How did density catch fool's gold?
By the heft: gold sits at 19,300 kg/m³, pyrite near 5,000 — nearly four times denser for the same handful. The panners did not need chemistry, only a consistent hand and the comparison; this page is that heft, with the arithmetic shown.
Is specific gravity unit-free?
Yes — density divided by density cancels to a pure number, which is why hydrometer readings and brewing gravities travel without units. 1.200000 here means 'twenty percent more crowded than water', and that sentence works in any units at all.
What does the volume card really answer?
The tank question: mass = ρ·V prices any container of the substance — a 200 L drum here weighs 240 kg, which is a fork-lift decision, not a detail. Density was never about the sample; it was the substance's price list per cubic metre.
Where does the 1.225 for air come from?
The International Standard Atmosphere: sea level, 15 °C, standard pressure. Real air moves with weather and altitude — thinner aloft, denser when cold — so quote 1.225 as the reference the aerospace world standardised, not the air outside your window.
Does density change with sample size?
Not for a pure substance: the kilogram doubles with the litre and the ratio holds. What changes it is temperature (things expand) and composition (things mix) — which is why the honest measurement notes both, and why brewers read gravity as a recipe thermometer.
How does this page hand off to buoyancy?
By handing over the number: buoyancy asks what the FLUID does with your displaced volume, and its arithmetic needs both densities — yours and the water's. This page measures the crowding; the buoyancy page prices the support.