Pre-Wash Shrinkage Planner
Plan cut sizes around expected first-wash shrink.
Size you want after washing.
Size you want after washing.
Override if you have tested it.
39.1 × 26.1 in
Cut this oversize so it shrinks back to your finished piece.
- Extra on width
- + 3.1 in
- Extra on length
- + 2.1 in
- Shrink applied
- 8%
Because shrink eats a percentage of the length, you divide the finished size by one minus the rate rather than simply adding the percent back. Wash and dry a scrap exactly as the finished garment will live, measure it, and feed that real rate in for the truest cut.
About This Tool
The Pre-Wash Shrinkage Planner tells you how much to oversize a cut piece so it still fits after its first wash, since most fabrics shrink before they ever become a garment. Enter the finished width and length you want, choose a fabric or type in a tested shrink rate, and the tool divides by one minus that rate to hand back the true cut size.
It works backwards from your finished measurement.
A fabric picker sets a sensible default shrink rate.
You can override that rate with your own test result.
The answer shows the extra to add on each edge.
It warns nothing is safe until a scrap is washed.
Pre-washed cottons still creep a little, so plan for it.
One honest cut saves a too-small finished garment later.
Why Pre-Wash Shrinkage Planner Math Matters
Cutting to the finished size means the first wash shrinks it small.
A garment that shrinks unevenly twists its side seams out of true.
Woven cottons and linens shrink far more than tight synthetics do.
Adding the raw percentage back is a common and costly error.
You must divide by one minus the rate, not add the percent.
Testing a scrap in your real dryer gives the honest number.
Pre-shrinking fabric before cutting removes the guesswork entirely and safely.
Planning shrink front loads keeps a gifted garment fitting for years.
The Formula
Cut size equals the finished measurement divided by one minus the shrink rate as a decimal, so a cotton that loses eight percent is divided by zero point nine two to give the oversize you cut before washing; because shrink takes a share of the length, simply adding the percent back would leave the piece slightly too small after the wash.
- finished —
- the size you want to remain after washing
- rate —
- the expected shrink expressed as a share of one hundred
- cut —
- the larger size you scissors before the first wash
The divide rather than the add is the whole trick, because a percentage of the longer cut piece is what disappears, so the number you remove is bigger than the number you would naively subtract.
Worked Example: Step by Step
- 1You want a tote panel that finishes thirty six by twenty four.
- 2Choose cotton, which the tool loads at an eight percent shrink rate.
- 3Enter thirty six for the finished width and twenty four for height.
- 4The factor is one minus zero point zero eight, so zero point nine two.
- 5Thirty six divided by zero point nine two is about thirty nine and a tenth.
- 6Twenty four divided by the same factor lands near twenty six.
- 7So you cut roughly thirty nine by twenty six before any washing.
- 8The readout shows the extra to add on width and on length.
- 9After a hot wash and dry the panel shrinks back toward target.
- 10Had you just added eight percent you would have cut a hair short.
- 11Wash a scrap first to swap the guess for a measured rate.
How to Use This Calculator
- Note the finished width and length the pattern asks you to reach.
- Pick your fabric so a typical shrink rate loads into the field.
- Override the rate with your own figure once you have tested one.
- Read the cut size and the extra added on each direction.
- Wash and dry the fabric, or a scrap, before you cut at all.
- Add the same allowance to every piece cut from that cloth.
- Recheck the finished size after the first wash to learn the true rate.
Key Terms
- Shrink rate
- the percentage of length or width a fabric loses in the wash
- Finished size
- the measurement a garment piece should hold after it has shrunk
- Cut size
- the larger oversize dimension you scissors before any washing happens
- Pre-shrinking
- washing fabric before cutting so it will not shrink a made garment
- Warp shrink
- lengthwise shrink along the selvage, often larger than crosswise
- Crosswise shrink
- shrink across the grain from selvage to selvage in a woven cloth
- Sewer's grain
- how straight a fabric lies, which uneven shrink can pull askew
- Sanforized
- a resin or mechanical finish that limits later shrinkage to about one percent
Pre-Wash Shrinkage Planner Reference Table
| Fabric | Typical shrink | Cut a little |
|---|---|---|
| Cotton | 6 to 8 percent | always |
| Linen | 8 to 10 percent | generously |
| Denim | 3 to 5 percent | modestly |
| Polyester | about 1 percent | barely |
The rates shown are friendly averages drawn from common woven and knit behaviour, not a guarantee, because a hot dryer shrinks far more than a cool wash, and a tightly woven or sanforized cloth shrinks less than a loose soft one straight off the bolt.
Common Mistakes & Pro Tips
- Adding the shrink percent back instead of dividing by one minus the rate.
- Cutting to the finished size and trusting the fabric will not shrink.
- Assuming the store label rate matches how you actually wash and dry.
- Ignoring that crosswise and lengthwise shrink differ on most woven cloth.
- Skipping the pre-wash on a garment destined for a hot tumble dryer.
- Using one rate for a lining and a shell fabric that shrink apart.
- Measuring a damp scrap instead of a fully dried one and reading low.
- Planning shrink after cutting instead of building it into every pattern piece.
- Treating a sanforized cotton like raw linen and oversizing it wildly.
Real-World Use Cases
- Sizing a tote or apron panel before the first hot wash.
- Cutting a cotton dress that must survive many launderings intact.
- Planning linen tea towels shrink-free to their finished dimensions.
- Ordering fabric with the extra shrinkage allowance built in upfront.
- Matching a lining and a shell that shrink at different rates.
- Teaching a beginner why pre-washing beats cutting to a pattern.
- Turning a measured scrap test into a reliable cut for a batch.
Pre-Wash Shrinkage Planner: Frequently Asked Questions
Why divide instead of just adding the percent?
Shrink removes a share of the longer cut piece, not the short finished one. Dividing by one minus the rate sizes the extra correctly, while merely adding the percent back leaves the piece a touch too small.
Should I pre-wash before cutting or plan a rate?
Either works, but pre-washing the whole bolt first is surest, since the fabric shrinks before you ever cut. Planning a rate suits when you must cut clean yardage that cannot be washed in advance.
How do I find my fabric's real shrink rate?
Cut a square, measure it, then wash and dry it exactly as the finished garment will live. Measure again once fully dry; that tested difference beats any chart average for honesty.
Does crosswise shrink match lengthwise?
Rarely, because a woven cloth usually shrinks more along the lengthwise grain than across. For critical garments, note both figures from a scrap test and size each direction with its own rate.
Do pre-shrunk fabrics still need an allowance?
A sanforized or labelled pre-shrunk cotton still relaxes a percent or two, so a small allowance is wise. Set that low rate in the tool, since even pre-washed cloth gains from a hair of extra room.
This page explains how the pre-wash shrinkage planner works, what each input means and where the numbers come from, so you can plan your next make with confidence.
Written by Bobbin & Form Editorial Team
Home sewists & machine-embroidery practitioners
Reviewed by Marie Delacroix
Custom sewist & machine-embroidery technician, 15 years at the machine
Formulas follow standard sewing and needlework references. Results are estimates — always confirm against your pattern and a pre-washed swatch.
Sources & further reading
- Threads Magazine — fabric cutting & yardage guides
- ISO 13934 — textile tensile & fabric property standards
- Your local fabric store's bolt-width charts