Calculator

Room size calculator

Enter a room's length, width and ceiling height and pick what it is for. The calculator gives the area and perimeter, checks the room against the IRC's minimums, and packs the furniture you tick into it to show how much floor stays free.

Open the 3-bed ranch Standard room sizes

Room size calculator

Feet and inchesMetres

Room type

Length

Width

Ceiling height

Measure inside the walls. The ceiling is checked as flat; the IRC checks are the 2021 model code, and your city or state may have amended it.

Floor area

144 ft²

48′ around the walls

69% of the floor stays free with the furniture in

Perimeter: 48′
Furniture: 31%
Free floor: 99 ft²

Furniture packed in, from above

not a layout

Floor taken and free

ft²

Queen bed33 ft²23%
Nightstand ×25 ft²4%
Dresser7 ft²5%
Free floor99 ft²69%

Pass: Area 144 ft² At least 70 ft² for a habitable room (2021 IRC R304.1; R312 in 2024).
Pass: Narrowest side 12 ft 0 in At least 7 ft in any horizontal direction (IRC R304.2).
Pass: Ceiling 8 ft 0 in At least 7 ft for habitable space (IRC R305.1; R313 in 2024), checked as a flat ceiling. Not checked: a sloped ceiling, which needs 5 ft or more over the required floor area and 7 ft over half of it (Exception 1), and beams or ducts in a basement, allowed down to 6 ft 4 in (Exception 3).
Pass: All 4 pieces fit Packed side by side; leave walkways of 30 to 36 in when you arrange them.

Open as a floor plan

The formula

Area: length × width, measured inside the walls.
Perimeter: 2 × (length + width).
Code minimums: a habitable room other than a kitchen needs at least 70 ft² (2021 IRC R304.1) and at least 7 ft in any horizontal direction (R304.2). Habitable space needs a 7 ft ceiling; bathrooms, toilet rooms and laundry rooms 6 ft 8 in (R305.1). The calculator checks the height you enter as a flat ceiling over the whole room. It does not check R305.1's exceptions, which need more than one height: a sloped ceiling, where the required floor area needs 5 ft and half of it 7 ft (Exception 1); a lower ceiling over bathroom fixtures that can still be used, with 6 ft 8 in over 30 × 30 in at a showerhead (Exception 2); and beams or ducts in a basement, down to 6 ft 4 in (Exception 3).
Furniture: the footprints of the pieces you tick, added up and packed into the room from one wall, largest first. What is left is the free floor.

Where the numbers come fromThe minimums are the 2021 International Residential Code, Sections R304 and R305 (ICC, checked 11 October 2026); the 2024 edition moved them to R312 and R313. Kitchens are exempt from the area and width rules, and bathrooms are not habitable rooms, so only the ceiling rule applies to them. Footprints: beds from the Sleep Foundation (queen 60 × 80 in, king 76 × 80); the 84 in sofa from Dimensions.com, with the 35 in sofa, 24 in coffee table and 17 in TV unit depths from our living room guide; tables and the 63 × 18 in buffet from dining room dimensions; 24 in deep base cabinets from kitchen cabinet dimensions; the 60 × 30 in desk from home office size; the 60 × 30 in tub, 30 × 21 in vanity and a toilet projecting 28 in from the 5 × 8 bathroom. The rest (nightstand, dresser and chair depths, the armchair, bookshelf, fridge depth) are the matching pieces in FloorGen's furniture library.

Worked example

A 12 × 12 ft bedroom with an 8 ft ceiling is 144 ft² with a 48 ft perimeter. It clears the 70 ft² and 7 ft minimums and the 7 ft ceiling. A queen bed (33.3 ft²), two nightstands (5.3 ft²) and a dresser (6.5 ft²) take 45 ft², 31% of the floor, leaving 99 ft² free. The same furniture in a 7 × 10 ft room, the smallest bedroom the IRC allows, leaves only 25 ft², 35% of the floor.

Rooms with the calculator's default furniture (worked with the calculator)
Room	Area	IRC R304 / R305	Furniture	Free floor
Bedroom, 7 × 10 ft	70 ft²	Passes, at the minimum	Queen, 2 nightstands, dresser: 45 ft²	25 ft² (35%)
Bedroom, 6½ × 12 ft	78 ft²	Fails: under 7 ft across	The same: 45 ft²	33 ft² (42%)
Bedroom, 10 × 10 ft	100 ft²	Passes	The same: 45 ft²	55 ft² (55%)
Living room, 12 × 16 ft	192 ft²	Passes	Sofa, coffee table, 2 armchairs, TV unit: 51 ft²	141 ft² (73%)
Dining room, 10 × 12 ft	120 ft²	Passes	Table for 6, 6 chairs, buffet: 41 ft²	79 ft² (66%)
Office, 10 × 10 ft	100 ft²	Passes	Desk, chair, bookshelf: 20 ft²	80 ft² (80%)
Bathroom, 5 × 8 ft	40 ft²	Not habitable; 6 ft 8 in ceiling	Tub, toilet, vanity: 20 ft²	20 ft² (50%)

Free floor is not the whole story

Walkways need to be continuous: 30 to 36 in for a main route, 24 in for a minor one (living room layout). Plenty of free floor in scattered pockets is not a walkway.
Doors and windows take wall you cannot put furniture against, and a door's swing takes floor.
A bedroom also needs an emergency escape opening and smoke alarms; see legal bedroom requirements.
Sloped ceilings change the area that counts: floor under a ceiling lower than 5 ft is left out (ceiling height requirements).

Questions

What is the minimum size of a bedroom?

70 ft² of floor and at least 7 ft in every horizontal direction under the IRC (2021 R304; R312 in 2024), with a 7 ft ceiling. A 7 × 10 ft room passes; a 6½ × 12 ft room fails even though it is bigger.

How do I calculate the square footage of a room?

Multiply the length by the width, measured inside the walls. For an L-shaped room, split it into rectangles and add them up; the square footage calculator takes several at once.

Does a kitchen have a minimum size?

Not under the IRC: kitchens are exempt from the 70 ft² and 7 ft rules. The useful numbers are work aisles of 42 in for one cook and 48 in for two (NKBA).

Is a bathroom a habitable room?

No. The IRC sets no floor area for a bathroom; its size comes from fixture clearances. Its ceiling may be 6 ft 8 in rather than 7 ft.

How much of a room should furniture take up?

There is no rule. What matters is clear walkways between the pieces and to the doors and windows; the calculator's free-floor figure is a quick first check before you arrange the room on a plan.