Why Did My Cake Sink in the Middle?
A cake sinks in the middle when it rises faster or higher than its structure can support, so the centre collapses before (or just after) the eggs and starch have set firm enough to hold it up. The usual culprits are underbaking, too much leavening, a temperature drop from opening the oven, an oven that runs cool, or too little flour. The good news: each one leaves clues, and each one has a simple fix.
Why do cakes rise and then fall?
A cake batter is a foam. Creaming butter and sugar, or whipping eggs, fills it with thousands of tiny air bubbles. In the oven, three things inflate those bubbles: the air itself expands as it heats, water turns into steam, and the leavener releases carbon dioxide.
At first, everything around those bubbles is soft and wet. It can stretch, but it can't bear weight. As the batter heats, egg proteins uncoil and bond together (protein coagulation), and the starch in the flour absorbs water and swells into a gel (starch gelatinisation). Both happen gradually as the batter climbs from about 60°C into the 80s and 90s (140 to 200°F). Once they've happened, the bubble walls go from stretchy to firm, and the cake holds its shape on its own.
So every cake is a balancing act between two timelines:
- The rise, driven by gas pushing outward.
- The set, driven by heat turning proteins and starch rigid.
If the rise outruns the set, or the gas shrinks before the set is complete, the middle drops. The edges, which heat and set first, stay put. That's why you get a crater rather than an evenly flat cake.
Chef Fizz says: A cake is a soufflé with better manners. It still needs to be set before you let it cool down.
What are the most common causes?
Underbaking
This is the number one reason. The outside looks golden and the edges have pulled away, but the centre is still soft. When you take it out, the hot gas inside cools and contracts, and an unset middle has nothing to hold it up. A sunken, dense, damp or gummy band near the bottom of the middle is the giveaway.
Check doneness properly:
- A skewer or toothpick in the centre comes out clean or with a few dry crumbs, not wet batter.
- The top springs back when pressed lightly.
- The edges have just begun to pull away from the pan.
- For certainty, an instant-read thermometer in the centre should read roughly 93 to 99°C (200 to 210°F) for most butter and sponge cakes.
Cakes also keep cooking a little from residual heat after they leave the oven, the same carryover cooking that happens with roasts, but that won't rescue a truly raw centre.
Too much leavening
It's tempting to think a bit more baking powder means a taller cake. Past the right amount, though, the bubbles grow so large and so quickly that their walls thin out, merge into bigger pockets and burst. The cake shoots up, often domes or even overflows, then deflates. The crumb is coarse and open, with a slightly bitter or soapy aftertaste. If you're working from a recipe you've scaled or converted, double-check those leavening amounts, and see baking soda vs baking powder for the right ratios.
Opening the oven too early
Opening the oven door can drop the temperature by 10 to 25°C (20 to 50°F) in seconds. Early in the bake, while the structure is still fragile, that cool air shrinks the gas and slows the set at the same time. The cake can sink in front of your eyes. Wait until at least two-thirds of the baking time has passed before checking, and use the oven light instead.
An oven that runs cool (or hot)
Home ovens are often off by 15°C (25°F) or more. A cool oven sets the structure too slowly, so gas escapes or the bubbles over-expand before the crumb firms up. A very hot oven sets the outside too fast: the edges and top crust over while the centre is still liquid and rising, so you get a peak or a crack that sinks as it cools. An oven thermometer is the cheapest baking tool that solves the most problems.
Wrong flour, sugar or liquid balance
Flour is a cake's main structural material. Too little and there's not enough starch and protein to build strong walls. Scooping flour by volume is unreliable; weighing it removes the guesswork.
Sugar and fat both tenderise by getting between proteins and slowing the set. Sugar also raises the temperature at which egg proteins coagulate and starch gelatinises. A little extra makes a moist cake; a lot makes a cake too weak to hold itself up. The guide on what sugar does in baking explains how much it really shifts the structure. Too much liquid, such as large eggs instead of medium, an extra splash of milk, or wet fruit, does something similar.
Mixing mistakes
Under-creamed butter and sugar give too few air cells, and the cake can be dense and sunken. Over-beating after the flour goes in can build excess gluten and trap extra air that collapses. Whipped egg foams, as in sponge or chiffon cakes, are fragile; folding too roughly knocks out the air the cake depends on, as anyone who has made meringue will recognise.
Want to quiz yourself on this? The Cooking Scientist app has a short lesson on why you shouldn't open the oven early, plus one on how eggs build a cake's structure.
How do I diagnose my sunken cake?
Cut it in half and look closely at the crumb.
| What you see | Most likely cause |
|---|---|
| Dense, wet or gummy band in the centre | Underbaked or too much liquid |
| Coarse, open, crumbly crumb; maybe a soapy taste | Too much leavening |
| Rose beautifully, then sank while baking | Oven door opened, or oven too cool |
| Cracked dome that collapsed after cooling | Oven too hot; outside set before inside |
| Low, heavy all over, slight dip | Under-creamed, old leavener or too little flour |
| Sank a little evenly on cooling | Normal; most cakes settle slightly |
A gentle settling of a few millimetres as the cake cools is completely normal. Hot gas shrinks and moisture escapes. A true crater is what you're trying to fix.
Does the pan matter?
Yes. Recipes are written for a specific pan size, and the depth of the batter changes everything. Pour batter for a 23 cm (9 in) pan into a 20 cm (8 in) pan and it's much deeper. The edges set long before heat reaches the centre, the middle stays liquid longer, and it's more likely to sink. As a guide, fill cake pans about half to two-thirds full.
Dark metal pans absorb more heat and set edges fast, sometimes before the middle catches up. Glass pans heat slowly but hold heat well. If you use glass, many bakers lower the temperature by about 15°C (25°F).
What about baking at high altitude?
Above roughly 900 m (3,000 ft), lower air pressure lets gas bubbles expand more easily, and water boils at a lower temperature, so batters rise faster and dry out quicker. Cakes rise dramatically and then fall. Common adjustments include reducing baking powder or soda by about a quarter, cutting sugar slightly, adding a little extra liquid and raising the oven temperature by about 8 to 14°C (15 to 25°F) so the structure sets sooner.
Try it at home
Find out what your oven is really doing. You'll need an inexpensive oven thermometer.
- Hang or set the thermometer on the middle rack, in the centre.
- Set the oven to 175°C (350°F). When the preheat signal sounds, note the thermometer reading through the window. Many ovens beep before they're truly at temperature.
- Wait another 15 minutes and read it again. This is your oven's real steady temperature. Is it higher or lower than the dial?
- Now open the door fully for 30 seconds, close it, and read the thermometer straight away.
Most people are surprised twice: first by how far off their oven runs, and second by how big the drop is after a short peek. That drop is exactly what a half-baked cake feels when you open the door to check on it.
Common mistakes
- Pulling the cake when it looks done. A golden top can hide a raw centre. Test with a skewer or thermometer in the very middle before taking it out.
- Adding extra baking powder for a taller cake. Too much gas makes bubbles burst and the cake collapse. Stick to the recipe's amount; for height, check your oven and pan size instead.
- Peeking early. Each opening drops the oven temperature sharply. Use the light and wait until at least two-thirds of the baking time has passed.
- Measuring flour by the cup. Scooping can give 20% more or less flour than intended. Weigh it, or spoon and level.
- Using a different pan size without adjusting. Deeper batter takes longer to set in the middle. Match the recipe's pan, or adjust the baking time and check doneness carefully.
- Using old baking powder. Weak powder gives a heavy, sunken bake. Test it in hot water; if it doesn't fizz hard, replace it.
- Jostling the cake mid-bake. Moving or banging the pan before it sets can knock out the gas. Rotate it only after the structure has firmed, if at all.
Questions
Why did my cake sink in the middle after I took it out of the oven?
Most often it was underbaked, so the centre hadn't set firmly enough to hold up once the hot gas inside cooled and shrank. Bake until a skewer comes out clean and the top springs back.
Can too much baking powder make a cake sink?
Yes. Too much leavening makes bubbles grow so large that they merge and burst. The cake rises fast, then collapses with a coarse, crumbly texture.
Does opening the oven door make a cake fall?
It can, especially in the first half to two-thirds of the bake. The rush of cool air shrinks the gas in the batter before the structure has set enough to hold it.
Can you fix a cake that has sunk?
It won't rise again once cooled, but you can trim the edges level, fill the dip with frosting or fruit, or turn it into a trifle. If it's still underbaked inside, return it to the oven briefly to finish setting.