For knit garments that are more complex than a basic T-shirt, the most reliable estimate before a marker exists is the panel method: calculate each panel's area, convert to weight with its fabric's GSM, and add allowances.
The formula#
For each panel:
- L, W: panel length and width in cm, including seam and hem allowances. Use the bounding rectangle of the panel.
- n: number of that panel per garment.
- GSM: finished weight of the fabric used for that panel.
Add the panels of each fabric, then add a wastage allowance per fabric.
Worked example: hoodie#
Size L hoodie in 320 GSM fleece, with 1x1 rib cuffs and waistband in 280 GSM.
Body fabric (fleece, 320 GSM)
| Panel | L (cm) | W (cm) | Qty | Area (cm²) |
|---|---|---|---|---|
| Front | 72 | 60 | 1 | 4,320 |
| Back | 72 | 60 | 1 | 4,320 |
| Sleeve | 66 | 46 | 2 | 6,072 |
| Hood side | 38 | 28 | 2 | 2,128 |
| Kangaroo pocket | 26 | 42 | 1 | 1,092 |
| Total | 17,932 |
Weight = 17,932 × 320 × 12 / 10⁷ = 6.886 kg/dz. With 12% wastage: 7.712 kg/dz.
Rib (280 GSM)
| Panel | L (cm) | W (cm) | Qty | Area (cm²) |
|---|---|---|---|---|
| Waistband | 96 | 16 | 1 | 1,536 |
| Cuff | 22 | 16 | 2 | 704 |
| Total | 2,240 |
Weight = 2,240 × 280 × 12 / 10⁷ = 0.753 kg/dz. With 10% wastage: 0.828 kg/dz.
The garment needs about 7.7 kg of fleece and 0.83 kg of rib per dozen. Each fabric is booked and costed separately. The hoodie consumption calculator runs this calculation.
Rectangles and real shapes#
Using bounding rectangles overestimates the area of shaped panels, such as sleeves and hoods. The wastage allowance then covers less real waste. Some factories use a lower wastage when the panel rectangles already include the shaped waste; others measure panel areas from CAD. Be consistent and compare estimates with actual cutting results.
Things to include#
- All fabric parts: hood lining, pocket facing, neck tape, placket and inside binding.
- Rib and trims: cuffs, waistband, collars.
- Size ratio: calculate for each size or use the ratio-weighted average.
- Tube width: if the panels do not fit the tube width well, waste rises.
- Shrinkage allowance for garment-washed styles.
Checking against actual cutting#
After the first cut, weigh the fabric issued and the fabric returned, and compare with the booked consumption:
Keep these records by style type. They are the best source for future allowances.
Common mistakes#
- Leaving out small panels such as pocket bags and facings.
- Using one GSM for body and rib.
- Wastage applied twice, once in panel sizes and again as a percentage.
- Size M consumption used for an order weighted towards larger sizes.
Use the knit fabric consumption calculator for any panel list, and see fabric consumption for the overall method.
Related guides#
- T-shirt fabric consumption: the quicker body block method for basic T-shirts.
- Fleece fabric: the fabric behind the hoodie example.
- Rib fabric: rib for cuffs and waistbands, costed separately.
- Garment costing: turning kilograms per dozen into fabric cost per garment.
- Marker making: checking the estimate against a real marker.
Frequently asked questions#
Should I include seam allowances in panel sizes? Yes. Measure panels as cut, including seam and hem allowances. Finished garment measurements understate the fabric used.
How much wastage should I add? Use your own cutting records for similar styles and fabrics. Wastage depends on tube or open width, marker efficiency, end loss, defects and shade grouping, so a single figure for all styles is rarely right.
Can I use this method for woven garments? You can estimate area the same way, but woven fabric is bought by length. Convert area to length using the cuttable width, or better, use a marker. See fabric consumption.