Goldsmith Calculator.

Carit is the goldsmith calculator built by a working bench jeweller for working bench goldsmiths. It covers the calculations you reach for every day at the bench - wax-to-metal conversion, alloy mixing, karat purity, ring weight, casting weight, live gold prices - in a single mobile app on iOS and Android. This page explains what each tool does and the formulas behind it.

What a goldsmith calculator is for

A goldsmith - whether working at the bench alone, in a workshop, or as part of a larger team - runs the same handful of calculations all day. Casting weights from a wax. Karat ratios when mixing from grain. Conversions between US, UK and EU ring sizes for sizing orders. Stone weights when a client asks about carat. Metal cost estimates for a quote. None of these are difficult on their own; put together, across fifteen or twenty jobs a day, the time compounds.

A goldsmith calculator collapses all those calculations into one place. It's not a general scientific calculator. It's not a gem-identification tool. It's a bench utility that assumes you already know goldsmithing and want to stop doing arithmetic by hand.

Carit's goldsmith calculator section covers six daily-driver tools that cover the vast majority of that arithmetic:

1. Wax-to-metal conversion

Weigh your wax model, pick the gold alloy, get the casting weight. The math is specific gravity × wax weight, and the specific gravities of the common gold alloys are well published: 24k pure gold is 19.32 g/cm³, 22k is 17.80, 18k yellow is 15.58, 18k white is roughly 15.45, 18k rose is 15.20, 14k yellow is 13.40, 10k is 11.55, and 9k is 10.90. Sterling silver is 10.36, fine silver 10.49, platinum 950 is 20.76, and palladium 950 is 11.90.

Multiply wax weight by the specific gravity of the target metal to get theoretical casting weight. Add roughly 2% for casting shrinkage and finishing loss. Carit's calculator handles the buffer automatically, so the number you see is the number to order.

Full reference table: metal weight calculator →

2. Alloy mixing

The alloy calculator tells you how much of each base metal to combine to hit a target karat and total weight. To make 100 g of 18k yellow gold, for example: 75 g of 24k gold plus 25 g of standard yellow master (a proprietary copper / silver mix). To make 100 g of 14k yellow from pure fine gold and master alloy: 58.3 g of 24k plus 41.7 g of master.

Carit's alloy calculator takes your target karat, target weight, and whichever base metals you have on hand, and outputs exactly how much of each to grain - saving the mental arithmetic or the "I'll just eyeball it and top up" habit that most bench goldsmiths know they shouldn't have.

Detail: alloy calculator →

3. Karat purity conversion

Every goldsmith knows the big numbers: 24k is pure, 18k is 75%, 14k is 58.3%. But what's 22k in percent? What's 16k? What's 750 parts per thousand in karats? Carit's karat tool handles the conversion in both directions - karat to fineness, fineness to karat - for every common goldsmithing purity.

4. Ring weight

Given inner diameter, outer diameter and band width, the ring weight calculator derives the volume of a plain band and multiplies by the specific gravity of the chosen alloy. Useful for quoting wedding bands, eternity rings, and any stock band where you know the target dimensions before cutting metal.

Volume of a plain band = π × ((outer radius)² − (inner radius)²) × width. Multiply that by the alloy's specific gravity for weight in grams.

5. Live gold prices

Carit pulls live gold, silver, platinum and palladium spot prices from market feeds, converts to your chosen currency, and displays them on the home screen so every calculation you run multiplies through the current metal cost. A 26 g 14k yellow-gold ring isn't just "26 g" - it's "$840 of raw material at today's spot", updated continuously.

Live metal pricing is a Carit Pro feature. The conversions and calculators themselves are free in the base app.

6. Stone weight estimation

Goldsmiths set stones. Setting stones requires knowing stone weight. Carit's carat weight calculator estimates the weight of round, princess, oval, cushion, emerald, pear, marquise, asscher, radiant, heart and trillion cuts from their mm measurements - using the standard industry carat-weight formula L × W × D × factor. Full reference: carat weight calculator →

Why use a dedicated goldsmith calculator?

You can do every one of these calculations on a scientific calculator, with a bench chart, and three minutes of arithmetic. But:

• You'll forget the specific gravity of 18k rose (it's a quiet 0.38 g/cm³ lower than 18k yellow) and order the wrong amount of grain.
• You'll convert UK size R to US 8¾ instead of 8.75 and scratch a wedding band by a quarter-size.
• You'll quote a 2 g wax at the 18k yellow rate when the client has asked for platinum, and the casting will be nearly twice the weight you budgeted.
• You'll forget to add 2% casting shrinkage and find yourself 0.5 g short at the finishing stage - the annoying, expensive kind of short.

A dedicated goldsmith calculator doesn't make you a better goldsmith. It makes the arithmetic invisible so you can spend your mental budget on the part of the job that actually requires you.

Who is the goldsmith calculator for?

Carit's goldsmith calculator is used by working bench goldsmiths, silversmiths, jewellery designers quoting their own pieces, casting houses handling client waxes, jewellery students learning to cost their work, and repair jewellers remaking or resizing. If you spend part of your day holding metal and the other part pricing it, the calculator saves you time on both.

It's probably not for pure 3D designers who never touch metal, retail consumers buying jewellery, or gemmologists doing appraisal work - there are better-targeted tools in those niches.

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