Cut a Gem Purity Calculator

Purity is the stat that separates a throwaway grind from a headline sale in Cut a Gem. Every geode enters your conveyor line with a baseline quality, passes through grinders that refine it, and may receive extra percentage boosts from totems placed on your plot. The geode’s tier — Basic, Dark, Crystal, or Prismatic — applies a multiplier that pushes high-investment setups toward the 100% purity cap Gem Traders advertises. Buyers then scale their offers based on that final number, which is why planning purity before you spend cash is smarter than buying the most expensive geode blindly.

This page explains how purity works in practical terms and gives you a live calculator to experiment with builds. Numbers are estimates for planning; in-game buyer RNG and future patches can shift actual offers.

What purity means in the sell loop

After geodes travel through your grinder line, the game outputs a gem with a purity percentage. Higher purity generally unlocks better negotiation starting points and higher accept thresholds. Cut a Gem also encourages you to reject bad offers when the UI allows, so knowing your expected bracket prevents accepting lowballs out of impatience.

Purity is not the only variable — gem type, buyer rotation, and temporary boosts matter — but it is the one you control most directly through equipment. That makes it the first metric worth modeling.

Inputs that affect your result

Four values drive the calculator below:

Base purity — Read this from the geode you are about to run or from tooltip text when available. Early Basic geodes start modestly; later tiers assume higher baselines before multipliers apply.

Grinder bonus — Sum the meaningful upgrade bonus along your active grinder chain. If you run multiple grinders, use the combined effect you expect on the batch you are calculating, not just the first machine you placed.

Totem bonus — Totems grant percentage boosts. Milestone codes such as 1MVISITS sometimes award totems directly, which makes this field important immediately after redeeming promo rewards on the Codes page.

Geode tier — Select Basic, Dark, Crystal, or Prismatic. Higher tiers carry larger multipliers in the formula, reflecting their shop price and rarity.

The widget combines these using a capped curve: bonuses from grinders and totems stack additively as percentages, tier multipliers scale the refinement term, and final purity cannot exceed 100%.

Use the calculator

Adjust the fields to match your current plot, then read the estimated purity and dollar band. Compare that band to buyer popups before you click Accept.

The estimated value row shows a low–high cash range derived from purity and tier — useful for relative comparisons even when the exact offer differs. Re-run the calculator whenever you buy a grinder upgrade, place a new totem, or switch geode tiers.

Step-by-step: planning a profitable batch

1. Check your cash and shop — note the geode tier you can afford repeatedly, not just once.
2. Enter base purity — use the stat shown for that geode type; if unsure, test twice with conservative and optimistic bases.
3. Add grinder bonus — include upgrades purchased on the belt path you will actually use for this batch.
4. Add totem bonus — include active totems; after code events, recalculate because free totems change this field dramatically.
5. Pick tier — match the dropdown to the geode family you selected in step 1.
6. Compare to buyers — if live offers sit far below the band, wait for a different buyer or improve purity before selling in bulk.

Repeat after every major purchase or patch noted on Latest Patch Notes.

Stacking grinders, totems, and tiers

Grinder and totem bonuses both enter as percentage contributions before the tier multiplier amplifies the refinement portion of the formula. That means totems reward players who already invested in grinders — a 10% totem on a weak line is less exciting than the same totem on a mature setup.

Tier jumps are step changes. Moving from Basic to Dark or Crystal is not a flat +5% feel; the multiplier reshapes the entire refinement term. Use the calculator to see whether a tier upgrade is worth the shop premium compared to spending the same cash on grinder levels.

Offline grinding and purity

Cut a Gem advertises offline grinder progress. Offline earnings still depend on the purity your layout can produce when you are away. If the calculator shows you plateau below rival players’ showcase gems, fix the layout before leaving the game AFK — otherwise you are accumulating mediocre stockpiles.

Limits and disclaimers

This tool is a fan wiki estimate, not a Gem Traders official API. Buyer offers can vary run-to-run. Patch notes on the Updates Hub may change coefficients without us knowing immediately. Use results to compare builds relative to each other, not as guaranteed sale contracts.

For broader strategy, pair this page with Getting Started and the Tools Hub as we add more planners.

When to recalculate

• After redeeming codes that grant cash or totems.
• After purchasing a new grinder tier or conveyor speed upgrade.
• After switching your main geode farm to a higher tier.
• After any patch mentioning purity, buyers, grinders, or totems.