Quick answer: how much backing do you need
Backing size equals top size plus 2 times overhang on each dimension. Panels come from usable fabric width, not nominal width. In this guide and in the calculator, fabric width means the width you can actually use after removing selvages. If you buy a 44 inch bolt, measure between the selvages after removing them, and enter that measured width, not 44, if it is less. Exact yardage is total length divided by 36. Yardage to buy is exact yardage rounded up to the nearest 1/8 yard, never rounded down.
Example: a 60 by 72 inch top, 4 inch overhang on each side, 44 inch fabric. Backing size is 68 by 80 inches in the entered direction. Panels equal 2. Total length is 160 inches. Exact yardage is 4.44 yards. Yardage to buy is 4.50 yards. Rotated direction: backing 80 by 68 inches, still 2 panels, total length 136 inches, yardage to buy 3.88 yards, so the calculator chooses the rotated layout. With 108 inch wide backing, panels equal 1 in both directions, and the rotated layout needs 68 inches, 2.00 yards to buy, against 80 inches, 2.25 yards, in the entered direction.
If you only need a number, use the Quilt Backing Calculator. If you want to understand why that number is right, and when to change the method, read on.
What quilt backing is, and why its size matters
Quilt backing is the bottom layer of the quilt sandwich. The top is the pieced design, the middle is batting, and the backing is the fabric underneath. When you quilt, all three layers are stitched together, so backing must be larger than the top. That extra size is called overhang, and it gives you room to quilt, trim, and bind without pulling the top out of shape.
Backing is not batting. Batting is soft and thick, and it sits in the middle. Backing is fabric, and it is measured and bought like fabric. If you mix the two up, you will buy the wrong thing, so keep them separate in your plan.
What you need before you start
- Quilt top width and length, measured flat, after pressing, in inches or centimetres.
- Overhang you want on each side. Four inches on each side is a common starting point for home quilting.
- Fabric width you plan to buy. Standard quilting cotton is 44 inches wide. Wide backing is usually 108 inches or 120 inches.
- Seam allowance for pieced backing, usually 0.5 inch, if you need more than one panel.
Step by step: how to calculate backing
Step 1: Measure the quilt top
Measure the finished top, not the size you hoped it would be. Measure width in two places and length in two places, and use the larger number for each, so a slightly uneven top still gets enough backing.
Step 2: Add overhang
Add overhang to both sides. For width, backing width equals top width plus 2 times overhang. For length, backing length equals top length plus 2 times overhang. If you add 4 inches on each side, you add 8 inches in total to each measurement.
Step 3: Choose your fabric width
Compare backing width with usable fabric width, not bolt width. Remove selvages first, measure the width that remains, and use that number for every step that follows. If backing width fits in one usable width, you need one panel. If it does not, you need piecing. Wide backing often removes piecing completely, but it is not always the cheapest choice, so compare both options before you buy.
Step 4: Work out panels
For straight piecing, the first panel gives you a full fabric width. Each extra panel adds fabric width minus seam allowance, because seam allowance is lost at each join. Round panels up. A part panel still needs a full panel of fabric, and rounding down is how backing ends up short.
Step 5: Convert length to yardage
Multiply panels by backing length to get total fabric length. Divide total length by 36 to get exact yardage in inches mode. Round up to the nearest 1/8 yard. Rounding up is not waste. It is the safety margin that covers cutting and trimming.
Try it with the calculator: Use the Quilt Backing Calculator with your own top size, overhang and fabric width. It uses the same steps as this guide, and it shows backing size, panels and yardage together.
Worked example: a twin quilt
Take a twin top that measures 68 by 88 inches. Add 4 inches of overhang on each side. Backing width is 68 plus 8, which is 76 inches. Backing length is 88 plus 8, which is 96 inches.
With 44 inch fabric and 0.5 inch seam allowance, backing width does not fit in one panel. Each extra panel adds 43.5 inches. Panels equal 1 plus the ceiling of (76 minus 44) divided by 43.5, which is 2 panels.
Total length is 2 times 96, which is 192 inches. Exact yardage is 192 divided by 36, which is 5.33 yards. Yardage to buy, rounded up to the nearest 1/8 yard, is 5.38 yards.
With 108 inch wide backing, panels equal 1, total length is 96 inches, exact yardage is 2.67 yards, and yardage to buy is 2.75 yards. Wide backing uses less fabric here, because it avoids a second panel, but wide backing is often priced differently, so check price per yard, not only total yards.
Backing size and yardage chart, our own computed table
This chart uses 44 inch usable fabric width and 4 inch overhang on each side, so backing size is top size plus 8 inches on each dimension. Usable width means width after removing selvages. It matches the Backing Calculator chart, and it is computed from the same panel rule, not copied from another site. Where rotation needs less fabric, the chart shows the rotated layout, because that is what the calculator chooses.
| Quilt size | Top size | Backing size | Panels | Yardage to buy |
|---|---|---|---|---|
| Baby | 36 by 48 in | 44 by 56 in | 1 | 1.63 yards |
| Lap | 50 by 60 in | 68 by 58 in | 2 | 3.25 yards |
| Twin | 68 by 88 in | 76 by 96 in | 2 | 5.38 yards |
| Full | 80 by 92 in | 100 by 88 in | 3 | 7.38 yards |
| Queen | 90 by 108 in | 116 by 98 in | 3 | 8.25 yards |
| King | 108 by 108 in | 116 by 116 in | 3 | 9.75 yards |
Note the Full, Queen and King rows: they need 3 panels, not 2. Check panel count carefully for a wide backing, because a calculator that only ever gives 1 or 2 panels will undercount a backing like this. If your backing width is wider than about 83 inches from 44 inch usable fabric, check for a third panel before you buy.
Borderline case that shows why the usable width definition matters: backing width 87 inches, seam 0.5 inch. With 44 inch usable width, panels equal 2. With 43 inch usable width, from a 44 inch bolt after removing selvages, panels equal 3. Same backing, different usable width, different panel count. This is why you must enter usable width, not bolt width, in the calculator.
Wide backing chart, 108 inch fabric
With 108 inch usable wide backing, most sizes need only 1 panel, because backing width fits in 108 inches. Yardage is still backing length divided by 36, rounded up to the nearest 1/8 yard. This table is computed the same way as the table above, not copied from a shop page.
| Quilt size | Top size | Backing size | Panels | Yardage to buy |
|---|---|---|---|---|
| Baby | 36 by 48 in | 44 by 56 in | 1 | 1.63 yards |
| Lap | 50 by 60 in | 58 by 68 in | 1 | 2.00 yards |
| Twin | 68 by 88 in | 76 by 96 in | 1 | 2.75 yards |
| Full | 80 by 92 in | 88 by 100 in | 1 | 2.88 yards |
| Queen | 90 by 108 in | 98 by 116 in | 1 | 3.25 yards |
| King | 108 by 108 in | 116 by 116 in | Does not fit in 1 panel | Piece it, or use 120 inch fabric |
King is the exception. Backing width 116 inches is wider than 108 inch fabric, so a single 108 inch panel cannot cover it, even though backing length fits. Do not buy a single king length of 108 inch fabric and hope it stretches.
The calculator tries both orientations for you
Orientation means which side of the top is treated as width. Some calculators only show one orientation, and that can hide a cheaper layout. The Backing Calculator now shows both directions and picks the cheaper one, so compare the two directions in its result, not by entering dimensions twice.
Worked comparison, twin top 68 by 88 inches, overhang 4, fabric 44, seam 0.5. Entered orientation: backing 76 by 96, 2 panels, total 192 inches, exact 5.33 yards, buy 5.38 yards, 1 seam. Reversed orientation: backing 96 by 76, 3 panels, total 228 inches, exact 6.33 yards, buy 6.38 yards, 2 seams. Entered orientation saves 1.00 yard and 1 seam here, so it is the better choice, unless seam placement on the back matters more to you than yardage. The calculator picks the entered orientation here automatically. The rule is simple: fewer panels and less yardage usually wins, but check where the seams will fall on the finished back before you decide.
Cutting and piecing, in brief
Remove selvages before you measure usable width, because selvage fabric is woven tighter and can shrink differently. Enter that measured usable width in the calculator, not the bolt width. Cut each panel to backing length, join panels right sides together with a 0.5 inch seam, press seams open to reduce bulk, then square the finished back and trim evenly from each side, so seams stay centred. A full step by step piecing tutorial is in How to Piece a Quilt Backing, and this section is only the cutting summary, not that tutorial.
Home quilting versus longarm quilting overhang
Four inches per side is a common starting point for home quilting. A longarm service often needs more, because the back must load on a frame and stay taut while it moves, and different services ask for different amounts. Ask the service before you buy, enter their number in the calculator, and do not use a home number for a longarm job. In centimetre mode, the same rule applies, with metres rounded up to 0.1 metre.
When to change the method
Three panels, not two
Use the panel rule, not a fixed panel count. Each extra panel adds fabric width minus seam allowance. Round panels up. A backing that needs 2.1 panels needs 3 panels of fabric, not 2 panels stretched to fit.
Diagonal piecing
Diagonal piecing can save fabric for some sizes, because the seam runs diagonally across the back instead of straight across. It is not always better, and it has its own limit. Use the Diagonal Pieced Backing Calculator for that layout, and do not apply the straight piecing panel rule to a diagonal back.
Pieced backing by design
Some backs are pieced on purpose, from scraps, fat quarters or leftover blocks, to make a second design on the back. That is a different project from a plain backing, with its own cutting plan. It is covered in full in How to Piece a Quilt Backing, not as a paragraph inside this guide.
Wide backing
Wide backing removes seams, but it does not remove overhang, squaring or price checks. A 108 inch fabric still needs 4 inches of overhang on each side, and a king top plus overhang can still be wider than 108 inches. Wide fabric choice is covered in full in Wide Quilt Backing Fabric.
Rotating the top, directional prints, and squaring
Rotating the top can sometimes save fabric, because backing length and width swap. The calculator now tries both orientations and chooses the layout that needs less fabric, and it shows both directions in the result, so you can see the saving. On a tie, it keeps the entered direction. Do not rotate a directional print freely, because flowers or animals printed sideways will show on the back. For a directional print, choose "Do not rotate" in the calculator. Square the fabric before you cut, and if the top was prewashed, prewash the backing in the same way, so the layers shrink together.
How to make sure your result is correct
- Usable width check. Subtract seam allowance from fabric width for every joined panel. If you used nominal width, your panel count is too low.
- Panel count check. Multiply panels by usable width, accounting for seams, and confirm the total covers backing width. If it does not, add a panel.
- Exact versus buy check. Buy yardage must never be below exact yardage. If it is, you rounded the wrong way.
- Overhang check. Confirm the overhang number with your longarm quilter, if one will quilt the top. Do not use a home quilting number for a longarm job.
- Final measure check. After piecing, measure the finished back flat. It must be larger than the top on every side, before trimming.
Standard width compared with wide backing
| Fabric width | Best for | What to watch for |
|---|---|---|
| 44 inches | Small quilts, and quilters who want a large choice of prints | Most larger quilts need piecing, and piecing adds seams on the back |
| 108 inches | Most twin, full and queen quilts, with one panel and no seam | Choice of prints is smaller, and price per yard is often higher |
| 120 inches | King quilts, and very wide tops | Availability is limited, so check stock before you plan around it |
Common mistakes that leave backing short
- Forgetting overhang. Measuring backing exactly the same size as the top leaves no room to quilt or trim.
- Using nominal width as usable width. A 44 inch fabric does not give you 44 inches of usable width after a seam, when it is joined to another panel.
- Rounding down. Rounding yardage down to a neat number can leave you a few inches short at the end of a panel.
- Mixing backing and batting. Batting is measured differently, and it is not a substitute for backing fabric.
- Ignoring longarm needs. If a longarm quilter will quilt your top, ask how much overhang they need, and use that number, not a home quilting number.
Tips from experienced quilters
Press and measure twice, especially if the top has borders that can stretch. If your top fabric was prewashed, prewash backing in the same way, so the layers shrink together, not apart. If you piece backing, press seams open or to one side consistently, so the back lies flat under quilting. Save the leftover backing. It is useful for binding tests, small projects, and repairs later.
Calculate your own backing now
Use your top size, overhang and fabric width in the calculator, and check the result against the steps in this guide.
Open the Backing CalculatorFrequently asked questions
Yes, many quilters do, especially for large quilts. Check the sheet size after washing, because sheets can shrink, and check that the fabric weight and feel suit your quilt top. A sheet does not remove the need for overhang.
No. If backing width fits in your usable fabric width, one panel is enough. Piecing is needed only when backing width is larger than usable fabric width, or when you want a pieced design on the back.
It depends on the quilter and the machine. Ask the quilter before you buy, and enter their overhang number in the calculator. Do not guess, because longarm loading needs more room than home quilting.
Do not stretch it to fit. Stretching pulls the top out of shape. Add a strip, piece an extra panel, or buy more fabric. A short backing is a problem at the last step, when fixing it is hardest.
It does not need to match exactly, but it should be similar in weight and care needs. Very heavy backing with a light top, or backing that shrinks differently, can make a quilt drape unevenly after washing.
Related guides and calculators
Next, read How to Piece a Quilt Backing for joining panels, and Wide Quilt Backing Fabric for choosing wide fabric. For a different layout, see the Diagonal Pieced Backing Calculator, and for the middle layer, see the Batting Calculator.