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- The standards we follow
The standards we follow
Every measurement, chart and calculation in SewNQuilt follows a published standard or a trusted industry reference. Here is the friendly tour, for sewists and quilters alike, in inches and centimetres.
What every number stands on
Units and conversions
One inch is exactly 2.54 cm and one yard is exactly 0.9144 m, the definitions set by the 1959 international yard and pound agreement and published by NIST. Every conversion in SewNQuilt starts from these exact values.
Imperial and metric are each planned natively. A quilt in centimetres gets its own cut list with a 0.75 cm seam, so every piece lands on a tidy number. Imperial cuts round up to the next 1/8 in, the marks on your rotary ruler, and metric cuts round up to the next millimetre.
Printing a PDF pattern? A4 follows ISO 216 and US Letter is 8.5 x 11 in. Print at 100 percent and measure the test square, usually 10 cm, often with a 3 in or 1 in square too.
Standards and references
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Stitch and seam types
Stitches follow ISO 4915:1991, the classification the garment industry uses worldwide (in the US, ASTM D6193 shares the same numbering). Class 300 is the lockstitch your machine sews: 301 for straight and 304 for zigzag. Class 500 holds the overlock stitches, such as the 504 three thread overlock.
Seams follow ISO 4916:1991, with eight classes from superimposed and lapped to bound, flat and edge finishing. A plain seam is written 301 1.01.01, the same language the workroom speaks. Stitch length reads both ways too: 2.5 mm is about 10 stitches per inch.
Piecing a quilt? Seams are sewn at 2.0 to 2.2 mm, about 12 to 13 stitches per inch, so they hold firm when later seams cross them.
Standards and references
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Body measurements and size charts
How to measure follows ISO 8559-1:2017, the international definitions of body measurements, alongside the size designation of ISO 8559-2:2025 and EN 13402 in Europe. Measure over the underwear you usually wear, keep the tape snug and level, and find the hip at its fullest, usually 7 to 9 in (18 to 23 cm) below the waist.
Size charts come straight from the pattern companies makers cut from: the US Big 4 (Butterick, McCall's, Simplicity, Vogue, New Look), Burda Style and OTTOBRE design. Your size profile picks the right size for each, including the high bust rule from the Big 4 fit guide: when bust minus high bust is more than 2 1/2 in (6.3 cm), choose by high bust.
Standards and references
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Seam allowances for sewing and quilting
US Big 4 garment patterns include a 5/8 in (1.5 cm) seam allowance, and UK and European envelope patterns include 1.5 cm (5/8 in). Burda Style magazine, OTTOBRE and Japanese pattern books are drawn on the stitching line, so you add 3/8 to 5/8 in (1 to 1.5 cm). Knits sewn on an overlocker use 1/4 to 3/8 in (6 mm to 1 cm).
Quilting uses a 1/4 in seam, with 0.75 cm as the metric convention. Every square is cut at its finished size plus 1/2 in (plus 1.5 cm in metric), so a 4 in finished square is cut 4 1/2 in and a 10 cm square is cut 11.5 cm. The app teaches the classic accuracy test: three 1 1/2 x 3 1/2 in strips (4 x 9 cm) sewn together measure exactly 3 1/2 in (9 cm) wide.
The golden rule in SewNQuilt: your pattern's own statement leads. Every project asks whether the allowance is included and remembers your answer.
Standards and references
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Needles and thread
Home machines take the 130/705 H needle system (also called HAx1 or 15x1). Needle size is written NM/US: NM is the blade diameter in hundredths of a millimetre, so 80/12 means 0.80 mm. Needle types and colour bands follow the SCHMETZ colour code chart, from Universal and Jersey to Jeans, Microtex and Quilting.
Thread is compared by Tex, the international measure in grams per 1000 m, because weight labels vary from brand to brand. For quilting, the familiar weights come from the thread makers' own charts: 50 wt cotton for piecing and 40 wt for standard machine quilting. A fresh needle for each new project keeps every stitch crisp.
Standards and references
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Fabric widths, fat quarters and precuts
Fabric maths starts from real bolt widths: quilting cotton at 42 to 45 in (107 to 114 cm), dressmaking fabric at 54 in (137 cm) and 58/60 in (147/150 cm), with 140 cm and 150 cm as the European standard widths, and wide backing at 108 in (274 cm). Fabric weight converts exactly too: 1 oz/yd² is 33.906 g/m². Fibre names follow ISO 2076 and EU Regulation 1007/2011.
A US fat quarter is a half yard cut in half at the fold, about 18 x 21 to 22 in. A metric fat quarter is half a metre halved, about 50 x 55 cm (20 x 22 in). Precuts follow the classic sizes: charm squares 5 in (12.7 cm), layer cakes 10 in (25.4 cm) and jelly roll strips 2 1/2 in (6.35 cm) by the width of fabric.
Shopping lists round up to the next 1/8 yd (11.4 cm) in North America and to the next 10 cm everywhere else, just the way fabric is sold at the counter.
Standards and references
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Quilt sizes by region and bed
Bed quilts start from the real mattress, with sizes for the US, Canada, the UK, Europe, Australia and Japan. A US queen mattress is 60 x 80 in (152.4 x 203.2 cm) and a European double is 55.1 x 78.7 in (140 x 200 cm).
Quilt width is the mattress width plus two drops, and quilt length is the mattress length plus one drop. Choose your look: topper 8 in (20 cm), coverlet 14 in (35 cm) or bedspread 21 in (53 cm), which also adds a 10 in (25 cm) pillow tuck.
Baby quilts are designed for play, tummy time, strollers and display, following the safe sleep guidance of the AAP, the NHS and Red Nose.
Standards and references
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Quilt unit maths
The well loved shop numbers come from exact geometry. Two at a time half square triangles are cut at the finished size plus 7/8 in (plus 2.6 cm in metric), so a 3 in finished HST starts from 3 7/8 in squares and an 8 cm one from 10.6 cm squares.
No waste flying geese use one large square and four small ones: 4 x 2 in geese start from one 5 1/4 in square and four 2 7/8 in squares, and 10 x 5 cm geese from one 13.7 cm square and four 7.6 cm squares. Each set makes four geese.
Binding is double fold, cut 2 1/4 in (5.5 to 6 cm) or 2 1/2 in (6.5 cm) wide, and its length is the perimeter plus 10 to 12 in (25 to 30 cm). Backing extends 4 in (10 cm) on every side for longarm quilting and 2 to 3 in (5 to 8 cm) for domestic machine or hand quilting.
Standards and references
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Care labels and quilt care
Care symbols follow ISO 3758:2023, the fourth edition, as published by GINETEX. Iron dots mean 248 °F (120 °C) for one dot, 320 °F (160 °C) for two and 410 °F (210 °C) for three. One bar under a symbol means mild and two bars mean very mild. In the US, the FTC Care Labeling Rule accepts the ASTM D5489 symbols, and the app reads both.
Every fabric in the library carries pressing and washing guidance built on that table, for garments and quilts alike. Finished quilts love cold or cool water on a gentle cycle with a mild detergent. Cotton batting may shrink 3 to 5 percent in its first wash.
Standards and references
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Our promise to every maker
Every figure in the app and on this site follows these references, checked and cited by our team. You get inches and centimetres side by side, each planned natively, in all ten languages. Sew and quilt with complete confidence.
Keep this with you
Save every result to a project, add fabric to your shopping list and work offline in the SewNQuilt app.