Bedding
Duvet and Comforter Size Calculator
Quick answer
How much drop you get on each side, and when to size up a comforter.
How much drop you get on each side, and when to size up a comforter. The formula is shown under the calculator, and every figure it uses is labelled as either an industry standard or a convention, so you can see which parts are settled and which are guidance.
Result
drop each side
- Mattress width
- 60 in
- Duvet width
- 90 in
- Drop each side
- 15 in
- Mattress thickness
- 12 in
The drop clears the 12 in mattress depth with 3 in to spare, which is usually enough to stay put.
The formula
Drop each side = (duvet width - mattress width) / 2. A duvet should clear the mattress depth plus a few inches to stay put.
Products for this answer
These re-order as you change the numbers above. Prices change often.
DOWNCOOL Comforters Queen Size
$22.99Queen duvet insert.
Check price on Amazon
Amazon Basics White Down Alternative Comforter and Duvet Insert with Corner Ta
$24.65Queen duvet insert with down alternative fill.
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Bedsure King Comforter Set Prewashed Soft Bedding Set 3Pcs Beige 104"x90"
$33.98King duvet insert.
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L LOVSOUL Queen Comforter Down Alternative Duvet Insert
$33.99Queen duvet insert with down alternative fill.
Check price on AmazonFrequently asked questions
How does the duvet and comforter size calculator work?
Drop each side = (duvet width - mattress width) / 2. A duvet should clear the mattress depth plus a few inches to stay put. The calculation runs in your browser as you type, and the working is shown line by line beside the result so you can check it against your own measurements rather than taking the number on trust.
Are these figures an industry standard or a convention?
The result is arithmetic on the numbers you entered, so it is exact for those inputs. What it is compared against is convention: thresholds like a comfortable bed height or a usable walking clearance are widely repeated guidance rather than measured standards, and the page says so wherever one is used.
What happens if I enter numbers outside the usual range?
It stops and says so rather than guessing. When the inputs fall outside what the published data supports, the result reads "Not enough to answer" instead of showing a confident figure. A disclaimer does not make a wrong number right, so returning nothing is the honest outcome when the underlying data does not cover your case.
Does this calculator store the numbers I enter?
No. Everything is computed in your browser and nothing you type is transmitted or saved. There is no account, no login and no record of your measurements. You can block cookies entirely and every calculator on this site will still work exactly the same way.
How to read the numbers on this page. Standard mattress and bedding dimensions are industry-wide and the same across manufacturers. Guidance like replacement intervals, firmness by body weight and walking clearance is convention rather than a measured standard, and every table here says which it is. Where a manufacturer does not publish a figure we leave it out instead of estimating. This is not medical advice: a mattress is not a treatment for a medical condition, and persistent pain is a reason to see a clinician.