This game-changing way to cut your kid's birthday cake will mean everyone gets a slice in their party bags (and there might even be leftovers for you)

You've been cutting your kid's birthday cake all wrong. This genius hack tried and tested by our Food Writer will ensure everyone gets a slice in their party bag...

Collage of images of a kid's birthday cake being cut for party bags
(Image credit: Future/Jessica Ransom)

Happy Birthday has been sung, the candles have been blown out, the kids are now occupied with a game of pass the parcel, and you're left with the responsibility of cutting the birthday cake and loading the party bags, but how do you go about it? 

Cutting the birthday cake can feel like a big responsibility, especially when there are party bags to fill, however, I've found a genius, game-changing way to cut a birthday cake which I just had to try myself - and it works! In this easy guide, I will explain how you can cut a cake into the most slices so you can share it with more people - and maybe even have leftovers for yourself.

When buying or making birthday cakes for kids, one of the most important things to consider is how many people it can serve and with this easy method, or should I say hack (yes, it's that nifty), you can optimise the number of portions and might even be able to get more slices than the suggested servings. 

For my cake-cutting test, I chose a cake that would serve 16, however by using this slicing and dicing technique, I managed to get at least 18 slices and could have got more if I cut the cake into 3x9cm strips. Tall cakes, like our tried and tested supermarket rainbow cakes, with lots of layers are perfect for this method because you can cut them in half widthways, doubling your slices again. Please note this method is for round cakes only, and may not be as effective with a different shaped cake, like a caterpillar cake for example.

How to cut a birthday cake

To try out this food hack for yourself, all you need is a round celebration cake and a large serrated knife. If you’re using a shop-bought cake they usually come on their own serving board but you could transfer to a plate or cake stand if you prefer. 

I find a serrated knife, such as a bread knife is best for cutting cakes but a large, sharp chef’s knife will be fine if that’s all you have. 

If you’re serving the cake straight away, make sure you’ve got plates and/or napkins to hand. You could also wrap the slices in clingfilm, tinfoil, or a napkin if you plan to give the cake away in gift bags. 

You will need:

  • A round cake
  • A large serrated knife

Step 1

Close up of two birthday cakes both being sliced

(Image credit: Future/Jessica Ransom)

Cut the cake in half across the centre. Then cut one half into quarters. 

Step 2

Collage images of cakes being sliced for party bags

(Image credit: Future/Jessica Ransom)

With the knife at a 90 degree angle, cut each quarter into slices or small strips.

Step 3

Slices of birthday cake on plates and boards

(Image credit: Future/Jessica Ransom)

Serve the cake and make sure you save a slice for yourself! 

What size slice is best for a kid’s party bag?

It depends on the number of slices you need to cut and how big the party bags are. If your bags are big and you’re feeling generous you can use the cake into thicker slices.

If you need the cake to feed more people, we’d recommend cutting the cake into thinner strips, approximately 3-4cm wide. If your cake is very tall and has lots of layers, you could cut the cake in half widthways too. 

What’s the best way to wrap a slice of birthday cake in a party bag?

Wrapping cake slices in cling film or foil will help keep it fresher and prevent it from drying out. However, if you think the cake is going to be eaten very soon after cutting, you could simply wrap it in a paper napkin. 

A more sustainable choice would be to use something like a reusable beeswax wrap, however, this may need to be carefully considered due to allergies.

How long should a cake sit before cutting?

If you’ve baked a cake and don’t plan on decorating it, it’s best to wait for the cake to cool completely before cutting it into slices. Cutting the cake while warm will result in crumbly slices that will not hold their shape.

Shop-bought ambient celebration or birthday cakes can be cut as soon as you remove them from the box and packaging. If the cake has fresh ingredients like whipped cream, it’s best to remove it from the fridge just before serving. As soon as you’ve blown out the candles and removed them from the top of the cake, you can start slicing it. 

Put any slices that aren’t being eaten straight away, back in the fridge. Ideally, they should be kept in an airtight container or plastic wrap to prevent the sponge from drying out too much. 

What I used in this feature and where you can buy it

M&S Raspberry Ripple Cake - View at Ocado 

M&S Raspberry Ripple Cake - View at Ocado 

For this feature, I bought this raspberry ripple celebration cake from Ocado by M&S. The box says it serves 16, but with this cutting method, I got at least 18 slices and could have gotten more if cutting it into approximately 3x9cm strips. It was a delicious cake with a sweet sponge and filling.

Victorinox Serrated Edge Pastry Saw - View at Amazon

Victorinox Serrated Edge Pastry Saw - View at Amazon 

I used a 26cm Victorinox serrated knife to cut the cake. It’s incredibly sharp and the long blade glides through the cake with ease. It’s also excellent for trimming pastry cases and cutting loaves of bread. Adults only. Keep well away from children as this is a very sharp knife.

Extra Strong 25.5cm Silver Cake Board - View at Lakeland

Extra Strong 25.5cm Silver Cake Board - View at Lakeland

If you’re making a cake from scratch, I’d recommend decorating it on a cake board like this one from Lakeland. This means you don’t have to worry about carrying a heavy plate to the party or venue and you can cut directly onto it without the worry of damaging your plate or cake stand.  Most shop-bought cakes come on a similar board but you could always transfer it onto this extra strong board if you like. 

Don't forget kid's party food - whether it's homemade or kid's party food to order, its always best to plan ahead.

You should check out these Frozen birthday cake ideas if your little one won’t let go of the hope for a homemade showstopper. Or perhaps these Bluey birthday cake ideas are more of their style. Or you could cheat and buy one of our tried and tested caterpillar cakes from your local supermarket?

You might also like these first birthday party ideas if this is your first experience of hosting. Plus, we have lots of fun kids' party games to get everyone involved. These 13th birthday party ideas are a great place to start if you want some ideas to impress your pre-teen and their friends. 

Jessica Ransom
Senior Food Writer

Jessica is a freelance food writer, stylist and recipe tester. She previously worked as Senior Food Writer at Future. While at Future Jessica wrote food and drink-related news stories and features, curated product pages, reviewed equipment, and developed recipes that she then styled on food shoots. She is an enthusiastic, self-taught cook who adores eating out and sharing great food and drink with friends and family. She has completed the Level 1 Associate course at the Academy of Cheese and is continually building on her knowledge of beers, wines, and spirits.