Steal an Egg Monster Chest Calculator: Flyswatter Drop Odds

Grinding the Hungry Monster Event in Roblox's Steal an Egg and wondering whether you'll actually pull the Flyswatter before your patience runs out? Our Monster Chest calculator turns your infested-egg haul into real cumulative odds, so you know exactly where you stand on the 5% weapon grind.

How the Calculator Works

The math is a standard independent-roll probability problem. Every 5 Infested Eggs fed to the Hungry Monster NPC produces 1 Monster Chest, and each chest rolls its reward table independently.

For any reward with a per-chest drop rate p, the chance of pulling at least one across n chests is:

Cumulative probability = 1 − (1 − p)ⁿ

The tool applies this formula to all five rewards on the Monster Chest table, then layers in the expected grind (the average number of chests or eggs needed for one drop, calculated as 1/p). It does not simulate bad-luck protection or pity — Steal an Egg's chests appear to be pure independent RNG.

Monster Chest Drop Rates

The full reward table the calculator is built on. Rates are community-reported (verification in progress) as of September 2026:

For the step-by-step feeding loop (find infested eggs → carry to base → feed the Hungry Monster → open the chest), see our full Flyswatter guide.

How Many Eggs Do You Need?

With a 5% Flyswatter rate, the milestones are:

• ~50% chance: 14 chests ≈ 70 infested eggs
• ~80% chance: 32 chests ≈ 160 infested eggs
• Expected (average): 20 chests ≈ 100 eggs per Flyswatter

The Monstrous Egg is far rarer at 1.5% — expect around 67 chests (≈ 335 eggs) per one. Most active players land a Flyswatter within 1–2 hours of dedicated farming. Use the calculator above to check your odds as your egg count climbs.

Frequently Asked Questions

How accurate are the drop rates?

They are community-reported from player testing as of September 2026 and the wiki notes them as "verification in progress." The probabilities the calculator shows are only as good as these input rates — verify against your own chest pulls and adjust your expectations if the game patches them.

Does the calculator account for bad luck protection?

No. It treats every chest as an independent roll using 1 − (1 − p)ⁿ. If Steal an Egg adds a pity system or escalating-rate mechanic later, the tool would need updating; for now, pure independent RNG matches community observations.

Should I keep farming past 32 chests?

Diminishing returns set in hard. Going from 32 to 64 chests only lifts your cumulative Flyswatter chance from ~80% to ~96%, doubling your egg cost for a 16-point gain. Past ~50 chests, you're statistically likely to already have one — if you don't, consider that the RNG just isn't with you this event.

Can I get the Flyswatter from regular eggs?

No — it only drops from the Monster Chest, which only comes from feeding 5 infested eggs to the Hungry Monster NPC. See the Flyswatter guide for the full flow.