What is the best mutation in Steal an Egg?

Rainbow, at ×3.5 income, with a roll weight of 1 in 100. Parasite is ×3, Fractured ×2.75, Golden and Spirit Bloom ×2.5, Bloom ×1.25, Silver ×1.2.

Roll weight 4 out of 100 at hatch, per the wiki. Silver is 6 out of 100 and Rainbow 1 out of 100.

Do size and mutation stack?

Yes — final income is base × mutation × size. The wiki's example: Rainbow + Huge on a $100/s pet is $1,750/s.

Can I add a mutation to an egg I already have?

Only Fractured, via a Mutation Consumable or the Rift Boss Shop's Mutation Shard, with a 10 % chance. It works on growing and fully grown eggs in your pen.

Does a bigger egg always earn more?

Yes, but with diminishing returns above 125× the pet's base weight, and bigger eggs are slower to carry.

How many hatches until a Rainbow?

On the wiki's 1-in-100 weight read as a per-hatch chance, there is roughly a 63 % chance of at least one Rainbow in 100 hatches and 87 % in 200 — our arithmetic, assumption stated on the page.

What is the difference between Bloom and Spirit Bloom?

Multiplier: Bloom is ×1.25, Spirit Bloom ×2.5. Both are Sakura-event mutations per the wiki, not natural rolls.

Guide

Steal an Egg mutations: every multiplier, roll weight and the size formula

Multipliers and roll weights are quoted from the wiki's Mutations page (edited 2026-09-09). Income examples are our arithmetic on those numbers.

Steal an Egg mutations are the reason two identical pets can earn amounts that differ by a factor of twenty. When an egg hatches the game rolls two independent traits: a colour mutation, which the wiki also calls an aura, and a size, shown as a weight in kilograms on the pet card. Both multiply the pet's base income, and they multiply each other. This page lists every mutation the wiki documents with its multiplier and how it is obtained, then walks through the size formula and the worked examples the wiki gives, so you can predict a pet's income before you commit a pen slot — or use the calculator, which does the arithmetic for you.

The mutation table

Seven colour mutations are documented. Three are normal hatch rolls with published weights; four come only from events or consumables. The wiki's phrasing for how each is obtained is preserved below.

Mutation	Income multiplier	How it is obtained (wiki wording)
Rainbow	×3.5	Animated rainbow effect. Extremely rare hatch roll — roll weight 1 out of 100
Parasite	×3	Not a normal hatch roll. From its own dedicated Parasite Egg, obtained through the feeding event
Fractured	×2.75	Not a normal hatch roll. Applied to an egg with a Mutation Consumable, 10 % chance
Golden	×2.5	Shiny metallic gold with coin particles. Roll weight 4 out of 100
Spirit Bloom	×2.5	Green spiritual effect. Currently unobtainable via normal roll — from the Sakura Incubator
Bloom	×1.25	Cherry blossom petal particles. Likely gated behind the Sakura event rather than normal hatching
Silver	×1.2	Shiny silver with metallic reflections. Roll weight 6 out of 100

Colour mutations (auras). Steal An Egg Wiki, Mutations page, edited 2026-09-09.

What the roll weights actually mean

The wiki gives weights, not percentages, for the three natural rolls: Rainbow 1, Golden 4, Silver 6, each 'out of 100'. Read literally, that is an 11-in-100 chance of any natural colour mutation on a hatch and an 89-in-100 chance of none. Rainbow at one in a hundred is why it carries the biggest multiplier; Silver at six in a hundred is the one you will actually see.

Those three weights and Roblox's badge statistics are the only probabilities in the entire register. There is no published hatch chance per pet or per rarity, and this site does not invent one.

Size: the multiplier that is easier to get

Size is rolled separately from colour, which is why the wiki says the same pet can appear as a Golden Giant or as a plain Huge with no colour at all. It is displayed as a weight in kilograms and, in the wiki's words, has a major effect on final income because size rolls are easier to obtain than rare colour mutations.

Every pet has a hidden base weight that correlates with its base income. Below 125 times that base weight, the wiki gives the income formula as base value × (actual weight ÷ base weight) to the power of 37/60 × the mutation multiplier. Above 125 times base weight, diminishing returns start: base value × mutation multiplier × (actual ÷ base) to the power of 2/5 × 125 to the power of 13/60.

The wiki translates the exponents for you: an egg at 100× base weight earns roughly 17× base value; at 200× roughly 23×; at 1,000× roughly 45×. Bigger eggs keep being worth more, but the gain per kilogram shrinks — and every extra kilogram is slower to carry home.

Income formula (from the wiki's Mutations page)

Final income = Base income × Mutation multiplier × Size multiplier

ratio = actual weight / base weight
if ratio <= 125:  size multiplier = ratio ^ (37/60)
if ratio >  125:  size multiplier = ratio ^ (2/5) × 125 ^ (13/60)

100× base weight ≈ 17× income · 200× ≈ 23× · 1000× ≈ 45×

The wiki's worked examples, and a few of ours

The Mutations page gives three combinations for a pet with $100/s base income: Normal $100/s; Golden + Giant = 100 × 2.5 × 3 = $750/s, a ×7.5 total; Rainbow + Huge = 100 × 3.5 × 5 = $1,750/s, a ×17.5 total. From those examples the size labels Giant and Huge correspond to ×3 and ×5.

Applied to real pets (our arithmetic, their multipliers): a Golden Giant Axolotl ($2.8K/s base) earns $21K/s. A Rainbow Huge Leviathan ($220K/s) earns $3.85M/s — more than a normal King Snake, the Secret of the next zone but one. A Silver Mutant Shark ($215M/s) earns $258M/s. A Rainbow Huge Nightflame (3B/s) earns 52.5B/s.

Pet (base)	Silver ×1.2	Golden ×2.5	Rainbow ×3.5	Golden + Giant ×7.5	Rainbow + Huge ×17.5
Axolotl ($2.8K/s)	$3.36K/s	$7K/s	$9.8K/s	$21K/s	$49K/s
Leviathan ($220K/s)	$264K/s	$550K/s	$770K/s	$1.65M/s	$3.85M/s
King Snake ($3.5M/s)	$4.2M/s	$8.75M/s	$12.25M/s	$26.25M/s	$61.25M/s
Mutant Shark ($215M/s)	$258M/s	$537.5M/s	$752.5M/s	$1.61B/s	$3.76B/s
Nightflame (3B/s)	3.6B/s	7.5B/s	10.5B/s	22.5B/s	52.5B/s

Example combinations. Base incomes from wiki infoboxes; multipliers from the Mutations page; products are ours.

Mutations you cannot roll: Parasite, Fractured, Spirit Bloom, Bloom

Four of the seven entries are not hatch rolls at all. Parasite (×3) comes from a dedicated Parasite Egg that the wiki ties to the feeding event. Fractured (×2.75) is applied after the fact with a Mutation Consumable and only works 10 % of the time; the Rift event page adds that the Boss Shop sells a consumable Mutation Shard with a chance to mutate an egg already in your pen, that it works on both growing and fully grown eggs, and that the chance is 10 %. Boss Mastery in the same event hands out eggs pre-loaded with Fractured. Spirit Bloom (×2.5) and Bloom (×1.25) are tied to the Sakura Incubator and Sakura event.

In other words, three of the four non-roll mutations route through events. When an event ends, so does the supply.

Choosing what to mutate

The maths says the multiplier is worth more on a bigger base, and a consumable with a 10 % success rate is a lottery ticket. So: spend Mutation Shards on the highest-base egg you have in a pen, not on the one you are fondest of. A 10 % chance of turning a $130M/s El Maja into a $357.5M/s Fractured El Maja is worth more than a certain ×2.75 on a Camel. And because size and colour are independent, a Huge egg with no colour is still the better shard target than a normal-size Golden.

Horizontal bar chart of the seven mutation multipliers from Rainbow ×3.5 down to Silver ×1.2, each annotated with how it is obtained — Mutation multipliers and how each is obtained, from the wiki's Mutations page (edited 9 September 2026). Chart: Steal an Egg Hub, from the Steal An Egg Wiki infoboxes (CC BY-SA 3.0, read 13 September 2026) and the Roblox Games API (read 17 September 2026).

What the wiki does not say

It does not list the base weight of any pet, so you cannot compute the ratio yourself from a card; it does not state the weight thresholds for the size labels beyond the Giant and Huge multipliers implied by the examples; and it does not give a probability for any size roll. Where this page says roughly, that is the wiki's word. Where a number is missing, it is missing.

Every natural roll on the top seven pets

The same three multipliers applied to the highest-income nest pets — our arithmetic on the wiki's incomes and multipliers, normal size.

Pet (base)	Silver ×1.2	Golden ×2.5	Rainbow ×3.5
Nightflame (3B/s)	3.6B/s	7.5B/s	10.5B/s
Kitsune ($1.8B/s)	$2.16B/s	$4.5B/s	$6.3B/s
Unicorn ($1B/s)	$1.2B/s	$2.5B/s	$3.5B/s
Gorilla King ($880M/s)	$1.056B/s	$2.2B/s	$3.08B/s
Oni Tiger ($600M/s)	$720M/s	$1.5B/s	$2.1B/s
Eternal Lunar Dragon ($250M/s)	$300M/s	$625M/s	$875M/s
Mosasaurus ($180M/s)	$216M/s	$450M/s	$630M/s

Silver, Golden and Rainbow on the top zone pets (normal size). Products ours.

What the roll weights mean over many hatches

If the wiki's weights are per-hatch chances — 1, 4 and 6 out of 100 — then the chance of at least one Rainbow in a run of hatches is 1 minus 0.99 to the power of the number of hatches (our arithmetic, on that reading). Ten hatches: about 9.6 %. Fifty: about 39.5 %. One hundred: about 63.4 %. Two hundred: about 86.6 %. For Golden the same numbers are 33.5 %, 87.0 %, 98.3 % and 99.97 %. The practical reading: a Rainbow is a long-run expectation, a Golden is a short-run one, and neither is something to plan a pen around.

Mutations by source, in one list

Where each of the seven comes from, since the question 'how do I get a Golden' has a different answer from 'how do I get a Fractured'.

Hatch roll (any egg): Silver 6/100, Golden 4/100, Rainbow 1/100.
After the fact, 10 % chance: Fractured, via a Mutation Consumable or the Rift Boss Shop's Mutation Shard, on a growing or grown egg in your pen.
Guaranteed: Fractured, from Boss Mastery rewards (eggs pre-loaded with the mutation).
Feeding event only: Parasite, from the Parasite Egg.
Sakura Incubator / Sakura event only: Spirit Bloom and Bloom.

Why size beats colour for most players

The wiki says it directly: size rolls are easier to obtain than rare colour mutations. The multipliers agree — Huge is ×5 and the best natural colour is ×3.5 — and they multiply, so a Huge Golden (×12.5) is worth more than a Rainbow of normal size (×3.5) by a wide margin. For a player deciding which egg to keep, the kilograms on the card are the first number to read.

Questions people ask

What is the best mutation in Steal an Egg?: Rainbow, at ×3.5 income, with a roll weight of 1 in 100. Parasite is ×3, Fractured ×2.75, Golden and Spirit Bloom ×2.5, Bloom ×1.25, Silver ×1.2.
How rare is Golden?: Roll weight 4 out of 100 at hatch, per the wiki. Silver is 6 out of 100 and Rainbow 1 out of 100.
Do size and mutation stack?: Yes — final income is base × mutation × size. The wiki's example: Rainbow + Huge on a $100/s pet is $1,750/s.
Can I add a mutation to an egg I already have?: Only Fractured, via a Mutation Consumable or the Rift Boss Shop's Mutation Shard, with a 10 % chance. It works on growing and fully grown eggs in your pen.
Does a bigger egg always earn more?: Yes, but with diminishing returns above 125× the pet's base weight, and bigger eggs are slower to carry.
How many hatches until a Rainbow?: On the wiki's 1-in-100 weight read as a per-hatch chance, there is roughly a 63 % chance of at least one Rainbow in 100 hatches and 87 % in 200 — our arithmetic, assumption stated on the page.
What is the difference between Bloom and Spirit Bloom?: Multiplier: Bloom is ×1.25, Spirit Bloom ×2.5. Both are Sakura-event mutations per the wiki, not natural rolls.