Petticoat Math!

Beware: Algebra Ahead!

Petticoats are not hard. I repeat, they are not hard. All of it is simple math and I’m here to help you figure out your fluff, length, and fabric requirements for a basic tiered petticoat like the one I’ve made for Anna!

First things first: Fabric. You’ll need a stiff organza as your base fabric, my suggestion is to use this from Fabric Wholesale Direct. It’s easy to sew, easy to cut (fun fact, you don’t have to cut organza, you just tear it on the grain so it’s always perfectly even!), and it’s pretty. The other fabric you’ll need is tulle for the bottom tier. You do not want net, it’s scratchy and too stiff. You really do want the flimsy apparel tulle.

Just the organza tiers are sewn together.

Next up: Figure out how long you want your petticoat. Measure from your waist to the point on your leg where you want the petticoat to end. Add 3” to the final length, this accounts the seam allowances you’ll need.

Say we want a floor length petticoat, for me that’s 41” from waist to floor length (ankle for petticoats). So I’ll add 4” to that to make it 45” in final length. (This is a very convenient number for the following number crunching you’ll need to make.)


The first thing you’ll want to figure out is the length of the tulle. The tulle is the bottom most tier of your petticoat and provides a clean line/ softness to the bottom. To figure this out, divide your Final Length by 3. In my case, a 45” final length divided by 3 is 15”. So now we know the width of the tulle: 15”. Guess what divides really nicely into 15” strips? 60” wide tulle fabric.

The next part figures out your tier widths. You’ll take your remaining final length, in my case, 30” (this is the 45” minus the width of the tulle which was 15”) and divide that into 3 even widths. 30” divided by 3 equals 10” wide.

Now we have all our widths! It’s that simple. For those who want to plug in their numbers into equations, here you go (and yes, this is legit algebra here folks):

Width of Tulle:

(Desired length is y) y/3 = x

Width of your tiers:

(Desired length is y) 2*(y/3)/3 = x

Now how do we figure out the length of the ruffles? That’s also pretty darn simple! Take your waist measurement and double it. So a 30” waist will equal 60” in length. That’s your first tier! Yay! One down, three to go! The next tiers are multiples of 1.5. So I’ll take that 60” and multiply it by 1.5 to get the length of the next tier, which is now 90”. The remaining tiers are all multiples of 1.5.

So my tiers for a 30” waist are:

Tier 1: 60”

Tier 2: 90”

Tier 3: 135”

Tier 4 (Tulle): 202.5 (I’m going to actually make that 200” instead for ease of measuring)

That’s the hard part. Use these equations for each layer of your petticoat, gather and sew them together with ½” seams, and you’ll have a nice fluffy tiered petticoat to go under a number of your costumes or even regular dresses/skirts. Once you’ve done all the math, figure out your yardage based on the width of the fabric you will be purchasing.

One note about the tulle at the bottom hem. You WILL want at least four stacked pieces of tulle on the bottom of each petticoat layer. In the picture below, I have 8 stacked pieces of tulle on the outer layer and 4 stacked pieces of tulle on the inner layer.

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