Quilting Measurement Converter and Decimal to Fraction Chart

Measurement converter

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Width-of-fabric converter

Many quilt patterns assume 42 inches of usable width. Our calculators use 40, because after shrinkage and trimming the selvages that is what many quilting cottons give. Wide backing fabric is usually 108 inches.

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How the conversions work

From	To	Do this
Decimal inches	Nearest ⅛ inch	Multiply the decimal part by 8 and round; the result is the number of eighths
Decimal inches	Nearest ¹⁄₁₆ inch	Multiply the decimal part by 16 and round; that many sixteenths
Inches	Centimeters	× 2.54 (exact)
Yards	Inches	× 36
Yards	Meters	× 0.9144 (exact)
Strips at width P	Strips at width Y	Strips × P ÷ Y, rounded up
Yardage at width P	Yardage at width Y	Yards × P ÷ Y, rounded up to the next ⅛ yard

For example, 3.3 inches is 3 plus 0.3, and 0.3 × 8 = 2.4, which rounds to 2: so 3²⁄₈, or 3¼ inches. On a sixteenth scale, 0.3 × 16 = 4.8, which rounds to 5, giving 3⁵⁄₁₆. Since 1959 the yard has been defined as exactly 0.9144 meter, which makes the inch exactly 2.54 centimeters, so those two factors are not approximations (see NIST Handbook 44, Appendix B).

When the fabric width changes the count

Strips multiply by the ratio of the widths only when they’re cut into pieces whose length doesn’t divide evenly. If the pattern cuts 2½-inch squares, a 42-inch strip and a 40-inch strip both give 16, and you need no extra strips at all. If it cuts 4½-inch pieces, a 42-inch strip gives 9 but a 40-inch strip only 8, and ten strips become twelve. Enter the piece length in the converter for the exact count.

Yardage converts by area, which is right for fabric that will become strips and pieces. It is wrong for one long piece. A backing has to be as long as the quilt plus a few inches whatever the width, so converting 6 yards of 42-inch backing to 2⅜ yards of 108-inch wide back only works if the quilt fits in 2⅜ yards of length. Use StitchTested’s backing calculator for backings, and the border calculator for borders cut along the length.

Decimal to fraction chart

Decimal to fraction chart for quilters (wtcquilt.com)

Sixteenths of an inch as decimals and millimeters:

Fraction	Decimal	Millimeters
¹⁄₁₆ in	0.0625	1.6 mm
⅛ in	0.1250	3.2 mm
³⁄₁₆ in	0.1875	4.8 mm
¼ in	0.2500	6.3 mm
⁵⁄₁₆ in	0.3125	7.9 mm
⅜ in	0.3750	9.5 mm
⁷⁄₁₆ in	0.4375	11.1 mm
½ in	0.5000	12.7 mm
⁹⁄₁₆ in	0.5625	14.3 mm
⅝ in	0.6250	15.9 mm
¹¹⁄₁₆ in	0.6875	17.5 mm
¾ in	0.7500	19.0 mm
¹³⁄₁₆ in	0.8125	20.6 mm
⅞ in	0.8750	22.2 mm
¹⁵⁄₁₆ in	0.9375	23.8 mm

Common decimals rounded to the nearest ⅛ and ¹⁄₁₆ inch. Add the whole inches in front (3.3 is 3¼ to the nearest eighth).

Decimal	Nearest ⅛	Nearest ¹⁄₁₆
0.05	0 in	¹⁄₁₆ in
0.10	⅛ in	⅛ in
0.15	⅛ in	⅛ in
0.20	¼ in	³⁄₁₆ in
0.25	¼ in	¼ in
0.30	¼ in	⁵⁄₁₆ in
0.35	⅜ in	⅜ in
0.40	⅜ in	⅜ in
0.45	½ in	⁷⁄₁₆ in
0.50	½ in	½ in
0.55	½ in	⁹⁄₁₆ in
0.60	⅝ in	⅝ in
0.65	⅝ in	⅝ in
0.70	¾ in	¹¹⁄₁₆ in
0.75	¾ in	¾ in
0.80	¾ in	¹³⁄₁₆ in
0.85	⅞ in	⅞ in
0.90	⅞ in	⅞ in
0.95	1 in	¹⁵⁄₁₆ in

Rounding tips

Round cut sizes up, not to the nearest, when the math comes from a square root, as with setting triangles and square-in-a-square centers. A piece an eighth too big trims; a piece an eighth too small doesn’t.
Don’t round each step. Work the whole calculation in decimals and round once, at the end.
A sixteenth of an inch is about the width of a pencil line. On a quilt with 40 seams across, losing a sixteenth at each one costs 2½ inches. That is why an accurate quarter-inch seam matters more than any conversion.
A quarter inch is 0.635 cm. If a metric pattern gives its own seam allowance, sew its cuts with that allowance; don’t mix metric cuts with a quarter-inch seam.

Related tools

For how many pieces you can cut from a fat quarter, charm square or yard, use the fabric yield calculator. Our guide to precut fabric lists the standard precut sizes, and what is a fat quarter explains how a fat quarter differs from a long quarter yard.

Quilting measurement converter