Circle Skirt Calculator
Enter your waist, skirt length and fullness to get the cutting radii and fabric size for a circle skirt.
For a circle skirt, the waist radius is the waist measurement divided by 2ฯ for a full circle (or by ฯ for a half circle). Add the skirt length to get the hem radius. A 28-inch waist gives a full-circle waist radius of about 4.46 inches, and you cut a circle of that radius with the length added all around.
How to Use This Calculator
Enter your waist measurement and the finished skirt length you want, then choose the fullness โ a full circle is the most dramatic and fabric-hungry, a half or quarter circle uses less. The calculator gives the waist cut radius (the small inner circle you cut out), the hem radius, and the size of fabric square you need.
Use the same unit throughout, and remember to add a seam allowance at the waist and a hem allowance at the bottom when cutting.
How the Calculation Works
A circle skirt's waist opening is an arc whose length must equal your waist. For a full circle that arc is a whole circle, so the radius is the waist divided by 2ฯ. A half-circle skirt spreads the same waist over half a circle, so its radius is larger โ the waist divided by ฯ โ and a quarter circle larger still.
Adding the skirt length to the waist radius gives the hem radius. The fabric must be at least twice the hem radius across (the full diameter) to fit the skirt, more for fuller styles that may need piecing.
waist radius = waist รท (2ฯ ร fullness); hem radius = waist radius + length
Worked Example
For a 28-inch waist, full circle: the waist radius is 28 รท (2ฯ) = 4.46 inches. With a 24-inch length, the hem radius is 4.46 + 24 = 28.46 inches.
The fabric needs to be at least 2 ร 28.46 = 56.9 inches square, so a 60-inch-wide fabric would just fit a full-circle skirt of this size in one piece.
Assumptions and Limitations
- Gives the cutting radii before seam and hem allowances โ add those yourself
- Fabric size is the minimum square for the chosen fullness
- Full circles often need two pieces if the fabric isn't wide enough
- Use a consistent unit for waist, length and fabric
Who Uses a Circle Skirt Calculator
Sewists and dressmakers use this to find the waist-cut radius and the fabric size needed for a full, half, or quarter circle skirt. Run it before cutting so the waist fits and you buy enough fabric. Enter your waist and length to get the radii and fabric dimensions.
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Open calculator โFrequently Asked Questions
How do you calculate a circle skirt radius?
Divide your waist by 2ฯ for a full circle, or by ฯ for a half circle. That gives the waist cut radius; add the skirt length to get the hem radius.
How much fabric does a circle skirt need?
At least twice the hem radius across โ the full diameter of the skirt. A 28-inch waist with a 24-inch length needs about a 57-inch square for a full circle.
What is the difference between full, half and quarter circle?
They set how much the skirt flares. A full circle is the fullest and uses the most fabric; half and quarter circles are progressively slimmer and more economical.
Do I add seam allowance?
Yes. The radii are the finished cutting lines, so add a seam allowance at the waist and a hem allowance at the bottom before cutting.
Why is my half-circle waist radius bigger?
Because the same waist length is spread over a smaller arc, the radius must be larger. A half circle uses waist รท ฯ, which is double the full-circle radius.
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