How do you scale up a pattern from a drawing?
Draw a grid over the small pattern, draw a bigger grid on the work, and copy square by square. How to work out the big square size, and what the scale factor tells you.
A 1/4"-square grid, 16 squares wide, blown up to 32" means drawing the big grid at 2" a square.
That is a scale factor of 8×, and the pattern comes out 20" tall.
How that is worked out
- Count the squares across the printed pattern rather than measuring it. The count is exact; a measurement off a photocopy is not.
- Divide the finished width you want by that count: 32" ÷ 16 = 2" per square.
- The height follows automatically — 10 squares at 2" is 20" — which is the whole advantage of the method: the proportions cannot drift.
Big-square size for a 1/4" grid pattern, by square count and finished width
| Squares across | 16" wide | 24" wide | 32" wide | 48" wide |
|---|---|---|---|---|
| 8 | 2" | 3" | 4" | 6" |
| 10 | 1 5/8" | 2 3/8" | 3 3/16" | 4 13/16" |
| 12 | 1 5/16" | 2" | 2 11/16" | 4" |
| 16 | 1" | 1 1/2" | 2" | 3" |
| 20 | 13/16" | 1 3/16" | 1 5/8" | 2 3/8" |
| 24 | 11/16" | 1" | 1 5/16" | 2" |
Worth knowing
- Number the rows and letter the columns on both grids before you start. Losing your place halfway through a cabriole leg is how a pattern ends up subtly wrong in one spot.
- Mark where the curve crosses each grid line, then join the marks freehand. Copying the crossings is accurate; trying to copy the whole curve by eye is not.
- A photocopier or projector is faster and this is still worth knowing, because both distort — a photocopier stretches slightly in the feed direction, and a projector has to be perfectly square to the surface or the pattern comes out trapezoidal.
- Cut one template in thin ply or hardboard, fair the curve with a spokeshave until it looks right, and use it for every copy. A fair curve matters more than a faithful one.
Work out your own numbers
- Grid enlargement calculator
Scale a small pattern up to full size using the classic square-by-square grid method.
- Circle and arc layout
A trammel arm's length for a full circle, or the radius of a shallow arc from its chord and rise.
Related questions
- How do you enlarge a pattern by hand?
- Draw a grid of equal squares over the small pattern, then draw the same number of larger squares on your stock. Mark where the outline crosses each grid line in the small version, put the same marks in the corresponding big squares, and join them. The square count carries the proportions for you.
- How do I work out the scale factor for a pattern?
- Divide the finished width you want by the width of the printed pattern, or more reliably by the number of squares across it. If a 16-square pattern has to finish 32" wide, each square becomes 2" — a factor of 8 over a 1/4" printed grid.
- Why are patterns printed on a grid?
- Because the grid is the instruction. It lets the pattern be enlarged to any size without a photocopier, and it survives being redrawn, reprinted and photographed at the wrong size — the squares are relative to each other, so as long as you count them the proportions come out right.