CraftM8 › QuiltM8 › How it works
How QuiltM8 works
Five rules, then a worked example. This is the same page the app carries — and the same discipline: every number below is computed by the engine when this page is built, so it cannot drift from what the app actually does.
Five things that are always true
1 · One question, one answer
Every tool asks the fewest things it can and shows the number as you type. There is no Calculate button and no wizard. If a tool needs something unusual, it is folded away under the conventions — with a sensible value already in it.
2 · Every size says whether it is a cut size or a finished size
This is where quilting maths goes wrong, so the app never leaves it to you to remember. A 6″ finished half-square triangle is cut at 6 7/8″ and trimmed to 6 1/2″ — three different numbers for the same triangle, and each is correct in its own place. Field labels say which one they mean, every time.
3 · Fabric always rounds up; counts round the way that is safe
Yardage rounds up to the next 1/8 yard — the smallest cut most shops will sell — so you are never told to buy too little. Cut sizes round up to the next 1/8″. How many strips you must cut rounds up; how many pieces fit a fat quarter rounds down. You will never be promised a piece that isn't there. And a total is rounded once, at the end — never cut by cut.
4 · You can always see the arithmetic
Every result has Show the maths underneath it: the numbered steps that produced the answer, with the assumptions used. Nothing is hidden and nothing is magic. Use it when a number surprises you — it is faster than re-deriving on paper, and if we are wrong you will be able to point at the step.
5 · A number that isn't exact says so
Most of the app is plain arithmetic, and arithmetic is either right or it is a bug — those answers carry no label, and they are checked against 6749 worked examples every time the app is built. An answer that depends on something nobody can know exactly — your shop's rate, the weight of your particular cotton — says Estimate, and tells you which figure is the soft one.
One tool, start to finish
The quilt is on the table: 60″ × 72″, finished. How much fabric to bind it, and how many strips to cut? Three fields, then the working — the book-style flat allowance, so you can follow it against any quilting book.
| Quilt width | 60″ | |
| Quilt height | 72″ | |
| Strip width (cut) | 2 1/2″ |
| 1 | Perimeter — 2 × (60" + 72") | 264" |
| 2 | Binding needed — 264" + 12" (corners & joins) | 276" |
| 3 | Strips — 276" ÷ 40" = ≈ 6 7/8 → round up | 7 |
| 4 | Fabric used — 7 × 2 1/2" | 17 1/2" |
| 5 | Fabric to buy — 17 1/2" → round up to the next 1/8 yd | 1/2 yd |
Cross-grain binding, cut across the width of fabric. One flat allowance for corners and joins, as quilting books print it.
Step 3 is where the rounding happens, and it rounds up: 276 ÷ 40 is 6.9 strips, and you cannot cut nine-tenths of a strip.
The mistake the example is protecting you from
Borders make the quilt bigger — a 3″ border on each side turns 60″ × 72″ into 66″ × 78″. Run binding on the finished size, after borders:
Three inches of border on each side added a strip and an eighth of a yard. Run binding on the finished size, after the borders — coming up short here is the single most common way to end up back at the shop.
Metric is recomputed, not converted
A German quilter does not think in 152.4 cm. The metric example is a 150 × 180 cm quilt on 110 cm usable fabric, buying in 0.1 m steps:
| 1 | Perimeter — 2 × (150.0 cm + 180.0 cm) | 660.0 cm |
| 2 | Binding needed — 660.0 cm + 30.0 cm (corners & joins) | 690.0 cm |
| 3 | Strips — 690.0 cm ÷ 110.0 cm = ≈ 6 1/4 → round up | 7 |
| 4 | Fabric used — 7 × 6.5 cm | 45.5 cm |
| 5 | Fabric to buy — 45.5 cm → round up to the next 1/10 m | 0.5 m |
Same rules, different world: the buying increment is 0.1 m, the cut grid is millimetres, and the answers are exact in both systems.
When a number looks wrong
Check these three first — between them they explain almost every surprise:
- Cut size or finished size? Roughly-half-an-inch-out is nearly always this. The app labels every field.
- Which size of quilt? Binding and backing want the finished size, after borders — see above.
- What width is your fabric? The app plans on 40″ usable — 42″ off the bolt, minus selvages and shrinkage. Change it on the tool, or once for every tool in Settings.
Still wrong? Open Show the maths. Every step has its arithmetic next to it, so you can see the exact line where our number and yours part company — and then tell us, because a checkable disagreement is the most valuable thing a user can send.