Why did my cake rise unevenly and come out lopsided?

Domestic ovens are not evenly heated, whatever the brochure says. Heat gathers at the back and the top and is thinnest just behind the door, so a tin shoved to the back of a shelf sits in a different oven from one in the middle. That is the first and by far the most common cause of a lopsided cake. The drawing shows the heat distribution in section, the tilted result, and the three other causes drawn beside it.

What you'll need

• A small spirit level, or a phone level app (optional)
• An oven thermometer (optional)

Step by step

1. Record which way the tin was facing.Before you do anything else, note which side of the cake rose highest and where that side was in the oven — back, front, left or right. Without that, you cannot separate an oven problem from a levelling problem.
2. Bake the next one centred, with clear space around it.Middle shelf, tin in the middle of the shelf, at least a hand's width to the oven walls and to anything above. Crowding two tins together blocks airflow between them and both cakes rise lower on the facing sides.
3. If it still tilts the same way in the room, check the level.Put a spirit level on the oven shelf, front to back and side to side. Ovens sit on adjustable feet and floors are rarely flat. A shelf that is out by a couple of degrees puts noticeably more batter on the low side before it sets.
4. Level the batter before it goes in.Spread it right into the edges and pull a little away from the centre, so the tin is very slightly deeper at the rim than in the middle. Batter finds its own level only until it starts to thicken, which is early.
5. Rotate at the right moment, not the wrong one.Turn the tin 180 degrees once the top has visibly set and stopped moving — usually past the two-thirds mark of the bake. Opening the door in the first half, while the crumb is still liquid and the raising agent is doing its work, causes a sunken middle instead.
6. Test the oven for a hot spot if the tilt persists.Cover a shelf with slices of white bread and grill-free bake at 180°C until they colour. The pattern of browning maps the hot spots directly. See `fix-an-oven-cooking-unevenly` for what to do about a bad one.

Tips

• Fan ovens are more even than conventional ones, which is exactly what they are for. If you have a fan setting and are not using it for cakes, see `fan-oven-for-baking`.
• A warped tin base rocks and holds more batter at one edge. Sit the tin on the worktop and press each corner — if it moves, it will bake tilted.
• A lopsided cake levels perfectly well with a serrated knife once cold. Cut with the cake on a turntable or a plate you can spin, and keep the blade horizontal rather than following the top.
• Loaf cakes tilt more than round ones because the tin is longer than the even zone of most ovens. Turn a loaf end for end rather than left to right.

Common mistakes

• Rotating the tin at the halfway mark by habit — For many sponges half-time is still inside the period where the structure has not set. The signal is the top no longer wobbling when the shelf is nudged, not the clock.
• Blaming the recipe — A lopsided rise is almost always geometry and heat, not proportions. The same batter baked centred on the middle shelf usually comes out level.

If it doesn't work