Hem Allowance Calculator
The number of folds is the number of times the fabric is spent. A double fold (2) turns the same depth up twice to bury the raw edge, so a 70 cm finished length with a 2 cm hem is cut at 70 + 2 × 2 = 74 cm. Overlock the edge and turn it once (1) and 72 cm is enough. Unlike a seam allowance, a hem sits at one end only, so nothing here is doubled for the opposite edge.
Your numbers
Cut length
74cm
Fabric turned under
4cm
Formula
Cut length = Finished length + Fold count × Hem depth
On a curved hem the excess has nowhere to go once the fold is deep: the inside gathers and ripples. Keep an A-line skirt hem under 1 cm, or finish it with bias tape. Knits want the opposite — a deep hem and a twin needle or zigzag, so the stitching can stretch with the fabric.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Finished length (cm)The length when finished. | 70 | 1 and up |
| Fold countHow many times the hem is turned up; a double fold is 2. | 2 | 1 ~ 2 |
| Hem depth (cm)The finished hem width — the height of one turn-up. | 2 | 0 and up |
Step by step
Quick reference table
Results when only Finished length (cm) changes and everything else stays put.
| Finished length (cm) | Cut length (cm) | Fabric turned under (cm) |
|---|---|---|
| 35 | 39 | 4 |
| 52.5 | 56.5 | 4 |
| 70 | 74 | 4 |
| 105 | 109 | 4 |
| 140 | 144 | 4 |
What each result means
| Result | At default values |
|---|---|
| Cut length (cm)The length to cut, finished length plus allowance. | 74 |
| Fabric turned under (cm)Length that disappears into the hem, which is what the cut length has to add. | 4 |
Common mistakes
On a curved hem the excess has nowhere to go once the fold is deep: the inside gathers and ripples. Keep an A-line skirt hem under 1 cm, or finish it with bias tape. Knits want the opposite — a deep hem and a twin needle or zigzag, so the stitching can stretch with the fabric.
Glossary
- Finished length
- The length when finished.
- Fold count
- How many times the hem is turned up; a double fold is 2.
- Hem depth
- The finished hem width — the height of one turn-up.
- Cut length
- The length to cut, finished length plus allowance.
- Fabric turned under
- Length that disappears into the hem, which is what the cut length has to add.
Frequently asked questions
Q. How is Hem Allowance Calculator calculated?
Cut length = Finished length + Fold count × Hem depth — The number of folds is the number of times the fabric is spent. A double fold (2) turns the same depth up twice to bury the raw edge, so a 70 cm finished length with a 2 cm hem is cut at 70 + 2 × 2 = 74 cm. Overlock the edge and turn it once (1) and 72 cm is enough. Unlike a seam allowance, a hem sits at one end only, so nothing here is doubled for the opposite edge.
Q. Can you walk through an example?
With Finished length 70cm, Fold count 2, Hem depth 2cm, the answer is Cut length 74cm.
Q. What do I need to enter?
Enter Finished length, Fold count, Hem depth. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Finished length (cm) moves the answer to Finished length (cm) 35 → Cut length (cm) 39 and Finished length (cm) 140 → Cut length (cm) 144. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
On a curved hem the excess has nowhere to go once the fold is deep: the inside gathers and ripples. Keep an A-line skirt hem under 1 cm, or finish it with bias tape. Knits want the opposite — a deep hem and a twin needle or zigzag, so the stitching can stretch with the fabric.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.