Ever wondered why warm, freshly made ring doughnuts taste so deliciously doughnut-y? Revealed for the first time, mathematician Dr Eugenia Cheng has found it’s all down to the Squidge Factor.


The ultimate doughnut is soft, billowing, comforting and ultimately - a bit squidgy. The squidgier, the better. Which is why the dough masters at Domino’s Pizza UK called on Dr Eugenia Cheng, Senior Lecturer of Pure Mathematics at Sheffield University, to find the squidge solution for their new doughnuts launching this month - with a bit of basic calculus.


Dr Cheng identified the ‘Squidgy to Crispy ratio’, which confirms that, all else being equal, the bigger the hole, the crispier the crust and the smaller the hole, the softer and squidgier the inside. Dr Cheng’s formula reveals that Domino’s’ Doughnuts have a squidgy to crispy ratio of 3.5 : 1 – based on an average hole size of 11mm.


Known for combining her passion for food with her love of maths, Dr Cheng commented: “This relatively small hole means that the Domino’s doughnuts are 78 per cent squidge and 22 per cent crisp – definitely squidgier than the average ring doughnut.”


“You imagine that as the doughnut grows, it has to keep adding on an infinitely thin surface area amount of doughnut, like putting on extra layers of clothing. Of course, there’s no such thing as an infinitely thin layer of doughnut around the outside—in reality it has some thickness. This is the crispy part around the outside.”


“We take the overall volume of the doughnut and then subtract the volume of the squidgy part on the inside, which is itself in the shape of a doughnut, with the same R (radius of doughnut) but smaller r (radius of dough.)”


Dr Cheng’s ‘Squidgy to Crispy’ ratio:

(r 2)2


4(r 1)


Simon Wallis, Sales and Marketing Director at Domino’s Pizza UK said: “After almost 30 successful years of delivering freshly baked hand-made pizzas, we’re now bringing the taste of the fairground to our customers’ front doors – and we’ve found the winning formula with our new ring doughnuts. The hole is integral to the ‘whole’ doughnut experience, so it makes complete sense that it affects the texture and taste. However, it doesn’t take a maths genius or science experiment to prove that our doughnuts are deliciously irresistible – you just have to try one.”