How the odds are calculated
Every number comes from two public sources, recalculated every night: what can be in a pack from MTGJSON, and prices from Scryfall.
What can be in a pack
A booster is filled from "sheets": weighted lists of cards, one per slot. A Play Booster might have seven common slots, three uncommon slots, a rare slot, a wildcard and a foil. MTGJSON publishes these sheets and how often each pack layout occurs, based on what Wizards of the Coast shares and on community research. For newer products, especially Collector Boosters, some of these weights are estimates.
Chance per pack and per box
The chance of a card in one pack follows exactly from the sheet weights. "1 in 216 packs" means a 1/216 chance per pack. The chance per box is the chance of at least one copy in a whole box: with 36 packs, a 1 in 216 card shows up in about 15% of boxes. Box sizes come from MTGJSON's product data where available.
Limited cards: no odds
Some cards have a fixed, small print run: numbered (serialized) cards, or a chase card such as the gleaming gold Smaug with about 500 copies. Wizards says how many exist, but not how many packs were printed, so nobody knows the chance per pack. We mark these cards "Limited print run", show "Odds not published" instead of a number, and leave them out of the expected value, the typical pack and the hit chances. A single guessed chance on a card worth thousands would otherwise move those numbers by several dollars.
Expected value and the typical pack
Expected value (EV) is the average market value of all cards in a pack: the price of each card times how often you get it. A few expensive cards pull the average up, so most packs are worth less. The median ("typical pack") is the value half of all packs stay under. The median and the chance of a $5, $20 or $50 card come from opening 100,000 simulated packs, the same ones every night, so they only move when prices move.
Prices
US prices are TCGplayer market prices in dollars, EU prices are Cardmarket prices in euros, both through Scryfall. Foil slots use the foil price. A card without a price in one market is not converted from the other; it counts as zero, and we warn when fewer than 85% of the cards you can expect have a price. Market value is not what you get when you sell: fees and shipping come off.
Pack and box prices
Sealed prices are the TCGplayer market price (through TCGCSV) and the Cardmarket price trend, collected every night. "138% of the pack price comes back in cards" compares the expected value with that price. It is an average: most packs return less, and selling cards costs fees.
History
The charts start with about 90 days of card prices from MTGJSON and grow by one day every night. Card prices are only kept for versions worth $1 or €1 or more. Sealed prices are kept from the day we started collecting them.
What is left out
- Tokens, art cards and ad cards are not counted.
- Colour balancing on common slots and the rule that a pack has no duplicates are ignored. For rares and mythics this makes no difference; for commons it barely does.