Simulate Archimedes' weighing experiment: weigh an object in air and water to find its volume, density, and identify its material from density tables.
The hydrostatic weighing method — first attributed to Archimedes — is one of the most reliable ways to determine an object's density and identify unknown materials. By weighing an object in air and then fully submerged in a fluid of known density, the apparent weight loss reveals the volume of fluid displaced, from which density is calculated.
This calculator processes the two weight measurements and computes object volume, density, specific gravity, and performs material identification against a table of twelve common metals and minerals. A confidence meter shows how closely the measured density matches the nearest known material.
Presets include classic experiments like the "Crown of Hiero" (testing if a crown is pure gold) and common lab samples. The step-by-step procedure table documents the experimental method alongside your actual measurements, making it ideal for lab reports and science education. It keeps the measured weights and the derived density together so the hydrostatic result is easy to verify. Check the example with realistic values before reporting.
Hydrostatic weighing is a fundamental laboratory technique in physics, materials science, and gemology. This calculator eliminates manual calculations and provides instant material identification, making it perfect for classroom experiments, quality control, and even verifying precious metals.
The step-by-step procedure table documents the entire method alongside actual measurements, which is invaluable for lab reports and science fair projects.
Volume = (W_air − W_fluid) / (ρ_fluid × g). Density = W_air / Volume. Specific gravity = ρ_object / ρ_fluid. Buoyant force = (W_air − W_fluid) × g.
Result: Density = 2700 kg/m³ → Aluminum
An object weighing 2.65 g in air and 1.67 g in water loses 0.98 g, giving volume = 0.982 cm³ and density = 2700 kg/m³ — matching aluminum exactly.
The most famous application of hydrostatic weighing is Archimedes' determination of whether King Hiero II's crown was pure gold. By comparing the crown's density to that of a pure gold reference, Archimedes could detect the presence of silver (density 10,490 kg/m³ vs. gold's 19,300 kg/m³). Even a 10% silver content would reduce the density to about 17,500 kg/m³ — easily detectable.
Hydrostatic weighing is used today in body composition analysis (measuring body fat percentage), gemstone authentication, industrial quality control of castings and forgings, and archaeological artifact analysis. The technique is valued for being non-destructive — the object is not altered in any way.
For very small or irregularly shaped objects, pycnometry (using a calibrated volume vessel) provides even higher accuracy than simple hydrostatic weighing. The pycnometer is filled with fluid, the object is added, and the volume of overflow is measured precisely. This variant can achieve density accuracy to four significant figures.
When an object is submerged, it experiences a buoyant force equal to the weight of displaced fluid. The apparent weight loss on a scale equals the mass of displaced fluid, which reveals the object's volume.
Yes — pure gold has a distinctive density of 19,300 kg/m³. If a gold-colored object has a significantly lower density (e.g., 15,000 kg/m³), it is likely gold-plated or alloyed with lighter metals. This is exactly how Archimedes reportedly tested King Hiero's crown.
With a 0.01 g precision balance and careful technique, you can determine density to within 1-2%. Sources of error include air bubbles on the surface, wire/string buoyancy, and temperature-dependent fluid density.
The suspension wire displaces a small amount of fluid, contributing to the apparent buoyant force. For precise measurements, subtract the wire's submerged volume from the total displaced volume.
Yes — any fluid of known density works. For minerals that react with water or dissolve, use a non-reactive fluid like mineral oil or ethanol and enter its density.
Gemologists use hydrostatic weighing to measure specific gravity, which helps distinguish natural gems from synthetics and identify gem species (e.g., diamond SG = 3.52, cubic zirconia SG = 5.80).