To age up a baby early in The Sims 3, buy a Birthday Inferno Birthday Cake from Buy Mode, then have a teen or older Sim use it to help the baby blow out the candles; the baby becomes a toddler on the spot. Left alone, babies also age up automatically when their baby stage runs out, and testing cheats can trigger it instantly. This guide covers all three methods, the lifespan settings that control the automatic birthday, and what to check when a baby refuses to grow.
Everything here is in the base game of The Sims 3, on PC and Mac.
Method 1: The Birthday Cake (Any Time)
The cake is the normal way to control when a baby grows up, and it does not have to be the baby’s birthday. Per community documentation, the Birthday Inferno Birthday Cake can age a Sim up one life stage at any time, and it works on any Sim on the lot, not just your own household.
- Buy the cake. In Buy Mode, sort by function and open Entertainment, then Parties. The Birthday Inferno Birthday Cake costs §30. Community documentation says the supermarket sells it too.
- Place it on a counter or table your Sims can reach.
- Click the cake with a teen, young adult, adult or elder and choose the option to help the baby celebrate their birthday. Babies cannot walk to the cake, so an older Sim carries them over.
- Watch the candles. The older Sim helps the baby blow them out, and the baby transitions to a toddler.
The cake has one candle for a baby. Community documentation notes a small (2 percent) chance the cake catches fire when the candles are blown out, so keep a smoke alarm in the room.
If you want guests, throw a proper birthday party with the cake as the centerpiece. Our guide to throwing and cancelling a party covers how to set one up.
Method 2: Let the Baby Age Up on Its Own
If you do nothing, the baby grows up automatically when its baby stage ends. Community documentation puts the baby stage at about three Sim days on the default lifespan. When the time comes, another household member will usually pick the baby up and help them with the birthday without any input from you.
How long that takes depends on your lifespan settings:
- Open the Options menu with the “…” button in the lower-left corner (EA’s help also lists F5 as the Options shortcut).
- Go to the Game Options tab.
- Check that aging is enabled, and use the lifespan slider to make every life stage longer or shorter.
A shorter lifespan means a shorter baby stage. If aging is switched off, babies stay babies forever unless you use a cake or the cheat.
Method 3: The Testing Cheat
For an instant age-up with no cake:
- Press Ctrl + Shift + C (or Cmd + Shift + C on the 64-bit Mac version) to open the cheat console.
- Type
testingCheatsEnabled trueand press Enter. - Shift-click the baby and choose Trigger Age Transition.
The baby ages up immediately. This also works on older Sims, so be careful not to click the wrong one. Our cheats guide covers the other Shift-click options.
When a Baby Will Not Age Up
- Aging is off. Check Game Options as above.
- Nobody can help. Babies need a teen or older Sim to carry them to the cake. A household with no eligible Sim at home cannot run the cake birthday.
- The Sim is stuck. If the baby or the parent is frozen mid-action, reset them with
resetSim FirstName LastNamein the cheat console. Our reset guide explains when that helps. - Custom content or mods. Broken mods can interfere with aging. EA’s help recommends launching with Run without custom content (under Installed Content in the Sims 3 launcher) to test whether custom content is the cause.
After the Birthday
Toddlers need to learn to walk, talk and use the potty, so this is when the real parenting starts. If you are planning the next baby, our guides to having a boy, having a girl and having twins cover the options. With Generations installed, community documentation says there is a good chance a relative mails the new baby an imaginary friend doll, which comes to life once they are older; our imaginary friend guide explains what happens with it.
Frequently Asked Questions
Can you age up a baby early in The Sims 3? Yes. A Birthday Inferno cake works at any time, and the Trigger Age Transition cheat works instantly.
Where is the birthday cake in Buy Mode? Sort by function, then look under Entertainment and Parties. It costs §30.
How long is the baby stage? Community documentation says about three Sim days on the default lifespan; your lifespan setting in Game Options changes that.
Who can help a baby blow out the candles? Any teen, young adult, adult or elder Sim on the lot.
Can a birthday cake catch fire? Rarely. Community documentation gives a 2 percent chance.
Browse the rest of our Sims coverage on the Sims hub.