Mattress Size Calculator & Guide
Find your perfect mattress size based on your height, sleeping style, room dimensions, and who shares your bed. Our calculator cross-checks three key factors to give you a data-backed recommendation.
How many people will sleep on this mattress?
This determines the minimum width you need.
Tell us about the sleepers
Height determines length; sleep style determines width.
What size is your bedroom?
We need at least 24" of walking space on each side. Large furniture needs 36".
How much space do you want?
This adjusts whether we recommend the snug minimum or the most spacious option.
Your inputs
No standard size fits all your criteria
Your combination of height, number of sleepers, and room size is tricky. Check the breakdown below to see what's closest, or consider rearranging furniture to free up space.
All sizes breakdown
How we calculated this
How the Calculator Works
Choosing a mattress size isn’t just about width. The right size is a three-way compromise between:
- Mattress length — tall sleepers need enough legroom
- Mattress width — solo vs. couple, sleep style, and pets
- Room space — the mattress must physically fit with walking clearance
Our calculator evaluates all three constraints simultaneously and recommends the largest size that passes every check.
Standard U.S. Mattress Sizes at a Glance
| Size | Dimensions | Best For | Min. Room |
|---|---|---|---|
| Twin | 38" x 75" | Children, single adults in small rooms | 7’ x 10' |
| Twin XL | 38" x 80" | Tall teens, college dorms, adjustable bases | 7’ x 10.5' |
| Full (Double) | 54" x 75" | Single adults, teens, guest rooms | 9’ x 10' |
| Queen | 60" x 80" | Couples, single adults who want space | 10’ x 10.5' |
| King | 76" x 80" | Couples who want room, co-sleeping families | 12’ x 10.5' |
| California King | 72" x 84" | Tall sleepers, narrow master bedrooms | 12’ x 11' |
Queen is the most popular size in America — roughly 47% of mattress sales. But “most popular” and “best for you” aren’t always the same thing.
Factor 1: How Tall Are You?
The standard rule of thumb: your mattress should be at least 8 inches longer than the tallest person sleeping on it. This accounts for a pillow at the head and natural movement during sleep.
- Under 5'4" — Any standard 75" mattress works (Twin, Full)
- 5'4" to 6'2" — You need at least 80" (Twin XL, Queen, King)
- Over 6'2" — California King (84") is worth considering
- Over 6'6" — You may need a specialty or custom size
If you’re exactly on the border, size up. Nobody regrets extra legroom.
Factor 2: How Wide Do You Need?
Width depends on how many people share the bed and how you sleep.
Solo sleepers
A single person technically needs about 24-30 inches of width — roughly shoulder width plus room to roll over. But comfort and sleeping style matter:
- Compact sleeper (fetal position, barely moves): Twin or Twin XL (38") is plenty
- Average sleeper (some movement): Full (54") gives breathing room
- Sprawler (arms out, starfish): Queen (60") or wider
Couples
When two people share a bed, each person’s slice of the mattress tells the real story:
- Full (54") = 27" per person — about as wide as a baby crib. Tight.
- Queen (60") = 30" per person — workable, but neither partner has room to sprawl
- King (76") = 38" per person — each partner gets their own Twin’s worth of space
If one partner is a restless sleeper, a King pays for itself in uninterrupted sleep.
Pets on the bed
Dogs don’t care about your personal space. Add roughly:
- Small dog (under 15 lbs): 12 inches
- Medium dog (15-50 lbs): 20 inches
- Large dog (over 50 lbs): 30 inches
A couple with a medium-sized dog on a Queen is effectively sharing a Full.
Factor 3: Will It Fit Your Room?
A mattress needs at least 24 inches of clearance on each walking side and at the foot of the bed. Without it, you can’t open drawers, walk to the bathroom at night, or clean under the bed.
Quick room-size rules
- Under 9’ x 10’ — Twin or Twin XL maximum
- 10’ x 10’ — Queen fits; King won’t
- 12’ x 12’ — King or Cal King with room to spare
- Under 8’ x 8’ — Consider a Murphy bed or daybed
If your room has large furniture (a dresser, wardrobe, or desk), you need even more clearance. The calculator accounts for this.
Mattress Size Comparison Chart
Width per person when sharing
| Size | Total Width | Per Person (2 sleepers) | Equivalent Solo Bed |
|---|---|---|---|
| Full | 54" | 27" | Smaller than a crib mattress |
| Queen | 60" | 30" | Narrow Twin |
| King | 76" | 38" | Full Twin |
| Cal King | 72" | 36" | Almost a Twin |
Length comparison
| Size | Length | Comfortable for heights up to |
|---|---|---|
| Twin / Full | 75" | 5'6" |
| Twin XL / Queen / King | 80" | 6'2" |
| California King | 84" | 6'6" |
Common Scenarios
Couple, both average height, 10’ x 10’ room
- Height check: 80" length is fine for anyone under 6'2"
- Width check: Two average sleepers need at least 51" — Queen (60") works
- Room check: 10’ x 10’ fits a Queen with 30" clearance on each side
- Recommendation: Queen
Tall solo sleeper (6'3"), small 9’ x 10’ room
- Height check: Needs at least 84" — only Cal King qualifies
- Room check: 9’ wide = 108" minus 48" clearance = 60" max width. Cal King is 72" — won’t fit.
- Compromise: Twin XL (38" x 80") is the only standard size that fits the room and offers 80" length
- Recommendation: Twin XL (or measure whether a Full XL at 54" x 80" could work)
Family of three (two adults + toddler), 12’ x 13’ room
- Width check: Two adults plus a child effectively need 70"+ of width
- Room check: 12’ wide easily accommodates a King
- Recommendation: King — each adult gets Twin-width space even with the child in the middle
Tips Before You Buy
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Tape it out. Mark the mattress dimensions on your bedroom floor with painter’s tape. Live with it for a day. You’ll immediately see whether walkways feel cramped.
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Measure twice. Bedroom dimensions on floor plans are often wall-to-wall. Account for baseboards, outlets, and radiator clearance.
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Think ahead. If you’re single now but might share the bed in 2-3 years, size up if your room allows it. Upgrading a mattress is expensive; buying the right size once is not.
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Check doorways and stairs. A King mattress is 76 inches wide. Make sure it can physically get into your bedroom. Measure hallway turns and stairwells.
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Consider an adjustable base. If you want an adjustable base, Split King (two Twin XLs) gives each partner independent head/foot adjustment on a King-sized platform.