Bed Size Calculator

Get a recommended mattress size from Twin to California King based on sleeper height and count, then see whether it fits your room with standard walking clearance.

Quick Facts

Length rule
Mattress length ≈ tallest sleeper's height + 6 in
Common guideline so feet don't hang off the end.
Standard sizes
Twin 38×75, Full 54×75, Queen 60×80, King 76×80, Cal King 72×84 (in)
Consistent across most U.S. mattress makers.

Your Results

Calculated
Recommended mattress size
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Smallest standard size that fits
Minimum length needed
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Height + 6 in buffer
Minimum width needed
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Based on number of sleepers
Room fit
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Bed footprint + clearance vs. your room

Ready

Enter sleeper and room details, then press Calculate.

Understanding Bed and Mattress Sizing

This tool recommends a standard U.S. mattress size from two simple factors — the height of the tallest sleeper and how many people will use the bed — then checks whether that size, plus a walking-space buffer, actually fits your room. It uses the industry-standard mattress dimension chart rather than a made-up scoring system, so every result maps to a real, purchasable mattress size.

The formulas

  • Minimum mattress length = tallest sleeper's height + 6 inches. This 6-inch buffer is a common furniture-industry rule of thumb so a sleeper's feet don't hang off the end of the bed. The result is then rounded up to the nearest standard mattress length (75, 80, or 84 inches).
  • Minimum mattress width = 38 inches (a Twin's width) for one sleeper, or 60 inches (a Queen's width) for two sleepers — the narrowest width most furniture guides consider comfortable for a shared bed.
  • Recommended size is the smallest standard mattress, by surface area, that meets or exceeds both minimums.
  • Room fit compares the recommended mattress's footprint, plus a 24-inch clearance buffer on the open sides, against your room's width and length in either orientation.

Standard U.S. mattress dimensions

  • Twin: 38 × 75 in — a single sleeper, kids' rooms, small guest rooms.
  • Twin XL: 38 × 80 in — a single sleeper who is 5'10" or taller; common in dorm rooms.
  • Full (Double): 54 × 75 in — one adult who wants extra room, or a snug fit for two.
  • Queen: 60 × 80 in — the most common size for couples and the largest that fits most bedrooms.
  • King: 76 × 80 in — two adults who want each about a Twin's worth of personal space.
  • California King: 72 × 84 in — narrower than a King but longer, favored by taller sleepers.

Why the clearance check matters

A mattress that fits a room "on paper" can still make the room unusable if there's no space left to open drawers, walk around the bed, or open a closet door. This calculator assumes at least 24 inches of open floor space is needed around the bed — a minimum commonly cited in interior-design guides — and flags when a room only meets that minimum versus has comfortable room to spare.

Frequently Asked Questions

How much longer should a mattress be than the tallest sleeper?
A common rule of thumb is that a mattress should be about 4 to 6 inches longer than the height of the tallest person sleeping on it, leaving room to stretch without your feet hanging off the end. This calculator uses a 6-inch buffer, then rounds up to the nearest standard mattress length (75, 80, or 84 inches).
What size bed is best for two people?
Queen (60 x 80 inches) is the smallest size most furniture guides consider comfortable for two adults, giving each sleeper roughly 30 inches of width. A King (76 x 80 inches) gives each partner close to 38 inches — about the width of their own Twin bed — which is why couples who move around during sleep often prefer it.
How much clearance space does a bed need in a room?
Interior design guides commonly recommend at least 24 inches (about 61 cm) of open floor space around a bed for walking room, with 30 to 36 inches being more comfortable where the room allows it. This calculator uses a 24-inch minimum when checking whether a bed fits your room dimensions.
What are the standard U.S. mattress sizes?
The standard sizes are Twin (38 x 75 in), Twin XL (38 x 80 in), Full (54 x 75 in), Queen (60 x 80 in), King (76 x 80 in), and California King (72 x 84 in). These dimensions are consistent across most U.S. mattress manufacturers.

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