Specimen Weight & Size Estimator
Enter a specimen’s dimensions and its mineral’s specific gravity to estimate its weight before you have it on a scale.
Estimated weight
When this estimate is useful
This kind of estimate comes up more often than you’d expect — guessing shipping weight from a seller’s listed dimensions, sizing a display case or shelf before a specimen arrives, or working out roughly how much a batch of rough will weigh going into a tumbler. Because density varies enormously across minerals — a fist-sized piece of galena weighs far more than the same size piece of opal — dimensions alone tell you very little without knowing what the specimen actually is.
The ellipsoid-and-packing-factor approach trades precision for speed: it’s built to get you in the right neighborhood from a tape measure, not to replace an actual weighing once the specimen is in hand.
Frequently Asked Questions
How does the estimator turn dimensions into a weight?
It models the specimen as a triaxial ellipsoid using your length, width, and height as its overall extents, computes that shape's volume, then multiplies by the mineral's specific gravity (its density relative to water) to get a mass. A packing factor scales the result down from a perfect ellipsoid to something closer to a real, irregular rough specimen.
What is the 'packing factor' and why isn't it 1?
A rough specimen is rarely a smooth, solid ellipsoid — it has flat faces, concavities, and broken edges that a bounding-box shape doesn't capture, so a factor of 1 (a perfectly solid ellipsoid) noticeably overstates the true volume. A default of 0.65 is a reasonable starting point for a typical irregular rough; blockier, more solid specimens sit higher, flatter or vuggy ones lower.
How accurate is this compared to just weighing the specimen?
Not as accurate — it's a planning estimate for when you don't have the specimen in hand yet, such as before a purchase, a shipment, or picking a display case. Once you have the actual specimen, a scale will always beat this calculation.
Where do I find a mineral's specific gravity to enter?
Common values are listed on the specific gravity calculator's reference bands, and most mineral reference guides list an SG range for each species. If you're not sure, our specific gravity calculator can measure it directly from an air-and-water weighing.
Educational estimate only — actual weight depends on the specimen’s real shape and any matrix or inclusions. Weigh the physical specimen whenever precision matters.