Free tool
Egg hatch odds calculator
Enter the drop weight of every pet in an egg and get each pet's hatch chance, its 1-in-N odds and how many eggs a player needs to open for a 50% or 90% chance of hatching it at least once. A pet's chance is its weight divided by the sum of all weights, so weights don't have to add up to 100.
Free, no sign-up · Updated
| Pet | Weight | Chance | Odds | Eggs for 50% | Eggs for 90% | In 100 eggs | |
|---|---|---|---|---|---|---|---|
| 60.0% | 1 in 2 | 1 | 3 | 100.0% | |||
| 25.0% | 1 in 4 | 3 | 9 | 100.0% | |||
| 10.0% | 1 in 10 | 7 | 22 | 100.0% | |||
| 4.50% | 1 in 22 | 16 | 51 | 99.0% | |||
| 0.50% | 1 in 200 | 139 | 460 | 39.4% |
Chance within
eggs
Chance = weight ÷ sum of all weights. Eggs for X% = the number of hatches after which a player has at least an X% chance to have hatched that pet once (no pity timer, no luck boosts).
How to work out egg odds
- List every pet the egg can hatch with its weight (any positive numbers: 60, 25, 10… or 0.5 for a legendary).
- Chance = weight ÷ total weight. A pet with weight 0.5 in a 100-weight egg hatches 0.5% of the time, or 1 in 200.
- Eggs for X% = ln(1 − X) ÷ ln(1 − chance), rounded up. For a 1 in 200 pet that is 139 eggs for 50% and 460 for 90%.
- Check the rarest pet against your egg price: eggs for 50% × egg price is what a typical player spends to get it.
- Add a pity timer or luck boosts if the 90% number feels too grindy; this calculator shows the odds without them.
Questions
How do you calculate hatch chance from weights?
Divide the pet's weight by the sum of all weights in the egg. Weights 60, 25, 10, 4.5 and 0.5 sum to 100, so the 0.5 pet has a 0.5% chance (1 in 200).
If a pet is 1 in 100, will I get it in 100 eggs?
Not for sure. After 100 eggs the chance of at least one is about 63%. You need 69 eggs for a 50% chance and 230 for 90%.
Do weights need to add up to 100?
No. Weights are relative: 6, 2.5 and 1 give the same odds as 60, 25 and 10. Many pet simulators use weights instead of percents so adding a pet doesn't mean rewriting every number.
Does this include pity timers or luck boosts?
No. It shows plain odds per egg. A pity timer guarantees a pet after N eggs, and a 2x luck boost roughly doubles the weight of the rare pets it applies to.
Read next
Fill your eggs with pets
Turn a prompt or a drawing into a rigged Roblox pet with a Gold, Diamond, Rainbow, Shadow and Neon rarity set.
60 free credits when you confirm your email. No card needed.