Blanket Size Guide: Calculate Your Coverage
Work out width, length and overhang separately, with examples for a measured 60 × 80 inch mattress.
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Measure your actual mattress
Measure across the top from side to side and head to foot. Decide whether the blanket should stop near the edges, drape down the sides or tuck underneath. A bed-size name is a starting point, not a replacement for those measurements. Include extra tuck allowance separately: our calculator models a simple draped layer.
Turn inches into the drape you want
Suppose the side of your mattress is 10 inches deep and you want the blanket to finish 2 inches below its lower edge. Your flat side allowance starts at 12 inches. If you also want fabric tucked under the mattress, add that separately. Measure the distance on your own bed: the frame and bedding arrangement can change where the edge looks right. Convert centimetres to inches by dividing by 2.54 before using the calculator.
The coverage formula
Blanket width = mattress width + twice the side overhang. Blanket length = mattress length + foot overhang. We assume the blanket starts at the head edge, with no extra head overhang. A fitted corner, deep mattress or tucked blanket may need different allowances.
| Measurement | Inches |
|---|---|
| Mattress width | 60 |
| Mattress length | 80 |
| Side and foot allowance | 12 |
| Blanket width: 60 + 12 + 12 | 84 |
| Blanket length: 80 + 12 | 92 |
Compare both dimensions separately
If your target is 84 × 92 inches, a blanket listed as 90 × 90 offers more width but less length than that target. Extra width does not compensate for missing foot coverage. This is a geometric example, not a recommendation for a particular model. Always check the actual measurements for the selected item.
Shared beds need a second check
The formula covers a flat bed. It does not account for bodies lifting the blanket or one person pulling it sideways. Use an existing blanket as a reference: if it repeatedly feels too narrow, record the additional width you want. Consider two separate blankets when coverage preferences differ rather than assuming a larger shared size solves every problem.
Remeasure when coverage is critical
Record initial dimensions and measure again after laundering according to the label. CottonWorks identifies several factors affecting dimensional change, so we do not add a universal shrinkage allowance. Keep model-specific tolerances where available and leave margin for your own coverage requirements.