How to Cut a Möbius Strip Through Your Bagel

February 22, 2016 | Elizabeth Knowles

Bagel cut into two interlocking mobius strips
Photo credit: And give yourself more cream cheese spreading room

And give yourself more cream cheese spreading room.

Bagels make a great breakfast, but with the hole in the middle, the spreading surface is limited. George W. Hart, a professor of engineering and mathematical sculptor, developed a cutting method to increase the spreadable area by dividing the bagel into two interconnected rings.

As shown in the video below, it takes four identical cuts to separate the bagel:


What you are doing when cutting it, is creating a double-twist Möbius strip cut. A Möbius strip is typically made by taking a strip of paper, twisting it once and re-attaching the ends so that if you draw a line on the paper and never lift your pen, you will make it all the way around the loop on both sides of the original piece of paper without crossing an edge — theoretically creating a loop with only one side.


Hart recommends choosing a bagel with as big a hole as possible to make the process easier. He also reminds you to move the bagel around every so often if you are putting it in a toaster oven so that it heats evenly.

How to cut a bagel into two mobius strips
Image Credit: Courtesy of George Hart

The real question is: is it worth it? How much more spreading room do you actually get? Mathematician Antonio R. Vargas has done the calculations, and they get quite complex, veering into calculus. On a webpage hosted by Dalhousie University, Vargas concludes that “the ratio of the surface area exposed by cutting along the two-twist Möbius strip to the area exposed by cutting the bagel straight in half is approximately: 1 + 1/6 (heights/width-height)2.”

To make a long story short, the amount of spreading surface you get depends on the size of your bagel, but it will always be more than if you had cut it in half.

Read next: How to Fairly Cut a Cake, According to Math

Hot Topics

Facebook comments