The math behind Case Split is simple, but it's worth understanding what the numbers actually mean. That way when someone in your group asks 'why is my share $87?', you can answer with confidence instead of hoping the spreadsheet is right.
Why not split evenly by card count?
Splitting a case evenly by number of cards kept sounds fair but usually isn't. Imagine a 200-card case where one person ends up with the single secret rare and 49 other cards, while another person gets 50 commons and no chases. If you split by count they pay the same amount — but one wallet is much happier than the other. Rarity weights fix this by giving each card a numeric share of the pool.
The formula
For each participant P, their cost is:
cost(P) = fixedCostsClaimedByP + (weightP / totalAssignedWeight) × (caseCost − totalFixedCosts)
Where weightP is the sum of rarity weights of cards P claimed, and totalAssignedWeight is the sum across all participants. Unassigned cards contribute weight to the total pool but no cost to any participant — which is why you'll see 'Unassigned weight' in the Split panel.
Picking weights everyone will accept
The single trick to picking weights is to talk about ratios, not absolute values. Instead of 'is a Mythic worth 1.5?', ask 'is a Mythic worth three commons?' If yes, and a common is 0.5, then a Mythic is 1.5. Group agreement on ratios is the actual work; the numbers you type into Case Split just encode the agreement.
A quick sanity check: multiply the average number of each rarity per case by its weight, then compare to what your group intuitively thinks each rarity is worth. If the numbers feel wildly off, tweak the weights before you open anything.
When to use fixed cost instead
Weights are for cards whose relative value is roughly known but not exact — a random rare is worth about the same as any other random rare. Fixed cost is for the few cards in a case that have a hard secondary-market price everyone agrees on. Alt Art chase cards, tournament staples, and confirmed hits belong in the fixed-cost column. Everything else is a weight.
Mixing the two isn't cheating — it's how you get an honest split without turning the case break into a pricing debate. The math handles both cleanly: fixed costs come out of the pool first, then weights divvy up what's left.
Common weight presets
Case Split ships defaults per game and lets you edit freely. Here are starting points our users report using:
- Magic: Common 0.3, Uncommon 0.5, Rare 1.0, Mythic Rare 1.7.
- Pokémon: Common 0.2, Uncommon 0.4, Rare 1.0, Ultra Rare 1.6, Secret Rare 2.0, Alt Art (fixed cost).
- Yu-Gi-Oh!: Common 0.3, Rare 0.5, Super Rare 1.0, Ultra Rare 1.5, Secret Rare 1.8, Ghost/Starlight (fixed cost).
- One Piece: Common 0.3, Uncommon 0.5, Rare 1.0, Super Rare 1.5, Secret Rare 2.0, Special Card Parallel (fixed cost).
Worked example
Case cost $300. Two participants. Ana takes 1 Mythic (weight 1.7) and 3 Rares (weight 1.0 each), total 4.7. Ben takes 1 Mythic (1.7), 4 Rares (1.0 each), and a $60 chase alt tracked as a fixed cost, total weight 5.7. Total assigned weight is 10.4. Fixed cost $60 comes out first, leaving $240 to split. Ana's share: (4.7/10.4) × $240 = $108.46. Ben's share: (5.7/10.4) × $240 + $60 = $191.54. Add them up: $300. Correct.