Circle skirt calculator
A full circle skirt for a 28-inch waist and a 22-inch length needs a waist radius of about 4.46 inches and just under 53 inches of fabric. Enter waist, length and fullness to get the cut, the hem length and the cloth area. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Waist
- 28
- Skirt length
- 22
- Fullness
- 1
- Waist radius
- 4.4563384066
- Outer radius
- 26.4563384066
- Fabric needed
- 52.9126768131
- Fabric area
- 2,136.53084434
A circle skirt is a donut of cloth: the inner hole is the waist, the ring width is the skirt length, and fullness says how much of a full 360-degree circle you use. This circle skirt calculator takes three positive finite numbers — waist measurement, skirt length, and fullness as a count of full circles (one is a full circle, one half a half-circle, one quarter a quarter-circle, three quarters a three-quarter, two a double) — and returns the waist radius of the inner cut plus the fabric needed, which is the diameter of the outer circle. Units stay whatever you send: inches in, inches out; centimetres in, centimetres out.
How waist radius and fabric needed are computed
A circle skirt is an annulus. The waist is not a hole of some guessed size: it is an arc of the inner circle whose length equals the waist measurement. Fullness is how many full circles that arc is taken from, so the inner radius is waist divided by two pi times fullness.
A full circle (fullness one) therefore has waist radius waist over two pi; a half circle (fullness one half) has waist over pi; a quarter circle has twice the waist over pi; a three-quarter circle uses two-thirds of two pi; a double circle halves the full-circle hole again. The outer radius is that waist radius plus the skirt length — the finished distance from the waistline to the hem.
Fabric needed is twice the outer radius, the side of the square you must cut from and the usual answer to how much cloth to buy when the bolt is at least that wide. The calculator also returns the worn fabric area, fullness times pi times the difference of the two squared radii, and the hem circumference, two pi times fullness times the outer radius, so you can buy hem tape or check swing.
A twenty-eight by twenty-two full circle therefore yields a waist radius of about four and a half inches and just under fifty-three inches of fabric; a twenty-six by eighteen half circle yields a larger hole and a longer cut.
Where a circle skirt fabric calculator earns its keep
Home sewists planning a twirl skirt need a number they can take to the fabric shop instead of standing at a sixty-inch bolt and guessing whether two yards will cover a twenty-eight-inch waist and a twenty-two-inch midi. Costume shops, dance studios, and theatre wardrobe rooms can drop the dancer’s waist, the requested length, and a fullness of one or one half into this calculator and hand the cutter a waist radius and a cut length in the same units as the rest of the takeoff.
Pattern-drafting classes can pin the formula and the example twenty-eight-by-twenty-two full-circle case in tests instead of recalculating two pi by hand each time the copy is edited.
What you can do with it
Home sewist midi full circle
Turn a 28-inch waist and a 22-inch length at fullness 1 into a waist radius of about 4.5 inches and just under 53 inches of fabric before you buy the bolt.
Dance studio half-circle cut list
From each dancer’s waist and requested length at fullness 0.5, print a waist radius and cut length the wardrobe room can mark without redrawing the annulus.
FAQ
What does fullness mean in the circle skirt calculator?
Larger fullness makes a smaller waist hole and more flare at the hem.
How is the waist radius of a circle skirt calculated?
Divide the waist by two pi times the fullness. For a full circle and a 28-inch waist that gives about 4.46 inches; a half circle doubles the radius because the waist arc only uses half of the ring.
How much fabric do I need for a circle skirt?
Twice the outer radius, which is the waist radius plus the skirt length. A full circle with a 28-inch waist and 22-inch length needs a square of about 52.91 inches, as long as the bolt is at least that wide.
Does the calculator add seam or hem allowance?
No. Nothing is added for ease, seams or hem. If you want a looser waist or a folded hem, add those lengths to the waist or to the skirt length before you calculate.
Can I measure in centimetres instead of inches?
Yes. Use any length unit you like, as long as waist and skirt length share it: centimetres in give centimetres out, inches in give inches out. Nothing is converted along the way.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/life/circle-skirt \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"waist":28,"skirt_length":22,"fullness":1}'const res = await fetch("https://api.kit.forhosting.com/life/circle-skirt", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"waist": 28,
"skirt_length": 22,
"fullness": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/life/circle-skirt",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"waist": 28,
"skirt_length": 22,
"fullness": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/circle-skirt", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"waist":28,"skirt_length":22,"fullness":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"waist":28,"skirt_length":22,"fullness":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/circle-skirt", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"waist": 28,
"skirt_length": 22,
"fullness": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "life.circle_skirt",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Zero, negative, missing, or non-finite values fail with invalid_input and are not billed.
How waist radius and fabric needed are computed
No ease, seam, or hem allowance is added: if you want two inches of ease at the waist or a one-inch hem, add those lengths to waist or skirt_length before you call.
Input contract, response fields, and validation errors
All three must be strictly positive. Numeric fields are rounded to twelve significant figures so tests stay stable across runtimes. POST a JSON body with three required finite numbers: waist, the waist circumference you will sew to, skirt_length, the finished length from waistline to hem, and fullness, the count of full circles. The fields also accept the aliases waist_measure and waist_circumference for waist, length and skirt for skirt_length, and circles and circle_count for fullness; the solver reads the first defined alias and reports errors against the canonical names so the web form can mark the right control. Units are caller-consistent and are never converted: inches in yield inches out, centimetres in yield centimetres out, and a mixed pair is treated as one system because this endpoint has no unit field. On success the body echoes the cleaned waist, skirt_length, and fullness, returns waist_radius and outer_radius, and gives fabric_needed as the primary yardage figure — the outer diameter — plus fabric_area and hem_circumference so a user interface can show cloth used and hem swing without recomputing them. A formula string restates the two-pi fullness rule and the diameter cut; a unit_note reminds clients to keep one linear system and that fabric_needed is a square side when the bolt is wide enough. Missing fields, empty strings, non-numeric tokens, NaN, Infinity, zero, and negative values all fail with invalid_input and a message that names the field; those failures are not billed. Successful API calls use the published base of $0.002 per item; the free browser path runs the same solve function without consuming prepaid balance.
Where a circle skirt fabric calculator earns its keep
Keep waist, skirt_length, and fullness positive and finite, pin the rounded fabric_needed and waist_radius fields in your tests, and you get a reproducible yardage figure for homework in a fashion course, a studio tablet, a production spreadsheet, or an edge worker without standing up a general pattern-drafting engine for a three-number sewing problem.
Integration use cases
Pattern-class checks and catalogue widgets
Grade student circle-skirt homework against a deterministic fabric_needed, or power a landing that answers how much fabric for a circle skirt with the same numbers the API later bills.
Technical questions
How do I calculate fabric for a circle skirt?
Send positive waist, skirt_length, and fullness (1 is a full circle). The API returns waist_radius as waist/(2π×fullness) and fabric_needed as twice the outer radius, plus fabric area and hem circumference.
How much fabric for a 28-inch waist and 22-inch full circle skirt?
A 28-inch waist, 22-inch length, and fullness 1 yield a waist radius of about 4.46 inches and fabric_needed of about 52.91 inches — the square side to cut from when the bolt is at least that wide.
What happens if waist, length, or fullness is zero or negative?
The task fails with invalid_input. Waist, skirt_length, and fullness must be positive finite numbers; zero, negative, missing, and non-numeric values are not billed.
What does the circle skirt calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.