Gem Weight Calculator (Free Online Tool) – Looking for feedback

[bernardx]

Hi everyone,

I noticed many questions here around “How many carats is my gem?” when only the dimensions are known. To help with this, I created a free online Gemstone Weight Calculator.

You just enter the gem’s length × width × depth (in mm), choose the gem type (sapphire, emerald, ruby, spinel, tourmaline, etc.), and it instantly estimates carat weight. The tool adjusts for each gem’s specific gravity to improve accuracy.

You can try it here: https://desireegems.com/pages/gemstone-weight-calculator

It’s not a replacement for professional weighing, but it’s useful for quick estimates when comparing stones or shopping online.

I’d love your feedback on it — especially from those of you who regularly measure stones. I’m also considering adding more tools (ring size converter, birthstone finder, gemstone care guide). Would that be useful?

Hope some of you find it handy!

— Bernard / Desiree Gems

 

[Autumn in New England]

For newbies who haven't yet invested in a gem scale, this is a wonderful tool. Or even just to roughly compare gem weights/sizes according to density, it's valuable. Thank you!!

 

[Garry H (Cut Nut)]

A tip - these formulae always under estimate weights.
Try 0.00625 for diamonds under 1ct as the girdle thickness is always adding more weight relatively.
Likewise the vast majority of gemstones have bulge - assume 5-10% more than the ideal formula and you will make people happy.
Under estimating can cause fights

 

[LilAlex]

That looks wonderful -- thank you!

To get at the bulging pavilion issue that @Garry H (Cut Nut) alludes to, I have always used the one at Dendritics. These are some of the data-entry options (I do not know the formulas they use but I think they are available on the site):