Bias Tape Calculator
A one-yard square of fabric gives about 16 yards of half-inch double-fold binding. The yield grows as the square of the side.
What a square of fabric gives you
Cut on the diagonal and joined continuously. The highlighted row is the smallest square that covers what you need.
A yard of fabric is about 17 yards of tape
People buy bias tape by the packet because a square of fabric does not look like much tape. The arithmetic says otherwise. Every square inch of the square becomes tape, so a square of side s cut into strips of width w gives about s² ÷ w inches of it. A 36″ square at 2″ strips is 596 inches — 16.6 yards — from one yard of fabric.
Which means the yield grows as the square of the side. Doubling the square quadruples the tape. Going from an 18″ square to a 36″ one takes you from about 4.1 yards to 16.6 — four times the tape from four times the fabric, which is obvious once stated and never is beforehand.
The figures here take 8 per cent off the theoretical area for the joining triangles at the ends of the tube, which is where the loss actually is.
Why bias, and why the cut width is a multiple
Fabric cut at 45 degrees to the grain stretches; fabric cut along the grain does not. That is the entire reason for bias binding — it will go round a curve and lie flat, where a straight-grain strip ripples on an outside curve and puckers on an inside one. On a perfectly straight edge, straight grain is fine and cheaper.
The cut width is a multiple of the finished width because of the folds. Single fold turns both raw edges to the middle, so it needs four times. Double fold does that and then folds in half again: six times. French binding is folded in half and applied doubled — also six times, and much harder wearing since two layers of fabric take the abrasion instead of one.
Cut widths
| Style | Cut width | |
|---|---|---|
| Single fold | 4× finished | Both raw edges folded to the middle. Cut four times the finished width. |
| Double fold | 6× finished | Folded to the middle, then in half again. Cut six times the finished width — the usual bought tape. |
| French / double bias | 6× finished | Folded in half lengthways and applied doubled. Six times the finished width, and much harder wearing. |
The length allowance here is 15 per cent over the bare perimeter, plus roughly two inches for each mitred corner. Running out of binding three inches from the end is a particular kind of misery, and the fabric it saves is worth pennies.
How to use
- Enter the finished width you want and the fold style.
- Enter the edge you are binding and how many mitred corners it has.
- Read the cut width and the total tape, joins and corners included.
- Take the highlighted square — the smallest one that covers it.
Frequently asked questions
How much bias tape comes from a square of fabric?
About the side squared divided by the strip width. A 36 inch square cut into 2 inch strips gives roughly 648 inches — some 16 yards after the joining waste — from a single yard of fabric. It is far more than it looks, which is why buying bias tape in packets is usually the expensive option.
Why does the yield grow so fast with the size of the square?
Because it depends on area, and area grows as the square of the side. Doubling the square quadruples the tape: an 18 inch square gives about four yards of 2 inch tape and a 36 inch square gives about sixteen. Every square inch becomes tape, so the total is simply the area divided by the width.
How wide do I cut the strips?
A multiple of the finished width, set by the folds. Single fold turns both raw edges to the middle and needs four times. Double fold does that and folds again, needing six times. French binding is folded in half and applied doubled — also six times, and much longer wearing since two layers take the wear rather than one.
Why cut on the bias at all?
Because fabric cut at 45 degrees to the grain stretches and fabric cut along the grain does not. Bias binding will go round a curve and lie flat; a straight-grain strip ripples on an outside curve and puckers on an inside one. On a genuinely straight edge, straight grain works perfectly well and wastes less fabric.
What is continuous bias?
A way of getting one long strip instead of many short ones. The square is cut once on the diagonal, the two triangles are joined the other way to make a parallelogram, that is sewn into a tube with a one-strip offset, and then cut in a spiral. It produces the entire yield as a single piece with the joins already sewn.
How much extra should I allow?
This page adds 15 per cent over the bare perimeter plus about two inches per mitred corner. That covers the joining seams, the overlap where the binding meets itself, and the fact that mitres eat length. Running out three inches from the end is a particular misery, and the fabric it saves costs pennies.
Where does the joining waste come from?
The triangles at the ends of the tube, which cannot be cut into full-width strips. That is why the figures here take about 8 per cent off the theoretical area rather than reporting it whole — the loss is real, small, and always in the same place.
Can I make bias tape without a special tool?
Yes. A bias tape maker is convenient and nothing more — pulling the strip through folds the edges for you while you press. The same result comes from pressing the strip in half, opening it, and pressing each raw edge to the centre crease. It is slower and identical.
What width should the finished binding be?
Quarter inch for garments and fine work, half inch for quilts and general binding, and wider for a deliberate feature. Narrower than a quarter inch is difficult to catch consistently on the underside; wider than an inch stops behaving like binding and starts behaving like a band.
Does the fabric need to be square to start?
For the continuous method, yes — the geometry depends on it. A rectangle works too but yields a little less for the same area because the diagonal is longer relative to the short side, and the offcuts at the ends are larger. Trimming to a square first is usually the simpler path.
Can I use this for quilt binding?
Yes, and the corner allowance matters most there. A quilt has four mitres and a long perimeter, so the 15 per cent plus corner allowance is doing real work — a quilt bound with exactly the perimeter length of tape will fall short every time.
Does this send anything anywhere?
No. Everything is calculated in your browser and nothing is stored or uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.