Sewing

Mathing is Hard

In honor of Pi Day (3/14), here’s a post about numbers.

I  was always pretty good at math, but after college and matrices and all kinds of weird statistics and shit, the math part of my brain shut down.

I don’t have kids so I didn’t know anything about Common Core math until one of my friends started raising hell about it on Facebook. I still don’t know what it is and from what I hear, I’m better off. Memorizing multiplication tables sounds a lot easier than drawing football fields with lines for each purple pancake, or whatever it is they do in schools now.

That being said, sewing requires a LOT of math. It’s really the simple kind, add 1″ here and there, multiply inches by 2.54 cm, etc. (Those using the metric system have it REALLY easy here, wish Americans would just switch over already!) But sometimes, you have to convert fractions into decimals or vice versa and that’s where things can get a little hairy.


Common sewing fractions are 5/8″ or 3/8″ for seam allowances, and I now know that those equal approximately 1.5 cm and 1 cm, respectively. Converting to fractions, 5/8 = .625 and 3/8 = .375 and you could memorize all of that if you really wanted to (and with time, I most likely will). But I’m an adult now, and with the math part of my brain on a semi-permanent Wharton Calculus-induced vacation, I’d rather preserve my brain cells for the important things, like remembering where I put my keys and what my husband’s name is (it’s Ryan, in case I forget). And so, as an adult, I’ve given myself that illicit holy grail of schooling: a cheat sheet!

I’ve started a Pinterest board specifically for Sewing Resources and these are my first pins to it. One is a conversion chart that shows the most common measurements (based on fractions of an inch) with the decimal conversion AND the corresponding metric measurement. It’s from a place that sells screws, so you can see how this information has cross-functional purposes (the functions being sewing and screwing, obvs).

The other pin is a decimal to fraction conversion calculator and THIS has saved my brain all week long. I’m currently working on my pants sloper and dividing funky measurements like 9 15/16″ by 4 isn’t easy math. Enter that into your Handy Dandy Sewing CalculatorTM and you’re going to be staring at a strange number that likely ends in 5 but that’s about all I can tell you. Actually the answer is 2.484375 and if you know what the fraction conversion is for that WITHOUT looking it up, then you win at life. I don’t, but the Handy Dandy Sewing CalculatorTM does and it will generously give us this:

And if you’re still a kid just now learning fractions, it will walk you through the steps of getting from A to B. I think this is actually supposed to be a teaching tool for math students, but I’m commandeering it for sewing purposes and that’s that.

I do, of course, know how to divide sixteenths by four in my head but it is SO MUCH EASIER to use a machine for it. I could also sew all of my clothing by hand, and weave all my own fabric, but we have fabulous machines for that too, so I’ll take the more efficient route on this as well.

Do you have any additional sewing resources to add? I want to add more pins to the board, so feel free to leave a link in the comments!

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