Floor plan guide
To measure a room for a floor plan, sketch its outline first, then go around it clockwise with a tape or laser, writing each wall's length and where every door and window starts and ends. Measure both diagonals to check the corners are square, add the ceiling height, and multiply length by width for the floor area.
This page is part of our floor plan guide. For what the finished drawing shows, start with what is a floor plan
A steel tape, a pencil and graph paper will do the whole job. A helper halves the time and most of the mistakes: one person reads, the other writes and repeats each number back.
| Tool | Good for | Watch out for |
|---|---|---|
| Steel tape measure, 25 ft (8 m) | Every wall, door and window. The default. | Sags on a long wall unless someone holds the far end. Where it backs into a corner, butt the case against the wall and add the length of the case, which many tapes print on the side. |
| Laser distance measure | Long walls, diagonals and ceiling heights, on your own. | Needs a solid surface to hit. Hold it level, with its base flat against the wall. Typical models are rated to about ±1/16 in (1.5 mm). |
| Phone measuring app | A quick first size, or checking a gap. | Small errors add up along a long wall, and tracking suffers facing a blank wall or in dim light. Check the longest wall with a tape before trusting the rest. |
| Graph paper and a pencil | The sketch that every number is written on. | Use pencil: the sketch changes as you find things you missed. |
Work around the room clockwise and read every number off the same tape. The sketch shows the finished floor plan measurements for a 12 ft 6 in by 15 ft bedroom.
Draw the outline freehand, large enough to write on, with every door, window, radiator and built-in where it sits. Letter the walls A, B, C and D clockwise, starting with the door wall. It doesn't need to be to scale: the numbers do that.
Face the wall and run the tape from its left-hand corner to its right-hand corner, along the top of the baseboard rather than the floor. Write the length outside the sketch, then move on to the next wall on your right.
Keep the tape anchored in the left-hand corner and read each edge as you pass it: where the door frame starts and ends, the window frame, the radiator. With everything measured from one zero, one misread doesn't shift the rest, and the last reading must match the wall length.
Draw each door's swing on the sketch: the side its hinges are on, and whether it opens into the room or out of it. Mark outlets, switches, the thermostat and heating or cooling vents too: they decide where a bed or a desk can go. If a window sill is low enough for furniture to sit under, note its height.
Measure corner to corner across the room, both ways. In a square room the two match; in the example both are 19 ft 6¼ in. If yours differ by more than about ½ in (1 cm), read the square check below before you draw.
Measure from floor to ceiling in two places. For a sloping ceiling, note the lowest and the highest point, and mark any beam or bulkhead on the sketch.
If you are measuring more than one room, measure each wall's thickness across a door frame. A North American interior stud wall is about 4½ in (115 mm). Leave it out and the rooms won't add up to the outside of the house.
Most measuring mistakes come from measuring to the wrong surface, not from misreading the tape. Measure the room itself, not the trim fixed to it.
| Measuring | Measure to | Not to |
|---|---|---|
| A wall | The wall surface at each corner, along the top of the baseboard | The baseboard itself, which shortens the wall by its thickness at both ends |
| A door | The inside edges of the frame, jamb to jamb | The outside edges of the trim around it |
| A window | The edges of the frame | The trim, the sill or the curtain rod |
| Ceiling height | The finished floor and the ceiling surface | A beam or a light fixture, unless you note it separately |
| Wall thickness | One wall surface to the other, across the door frame | Across the trim, which sticks out from the wall on both sides |
How doors, windows and their swings are then drawn on a plan is set out in floor plan symbols
Measure every wall in order, exactly as for a rectangular room: an L-shaped room simply has six walls instead of four. For the floor area, split it into rectangles.
In a room with square corners, the walls facing one way add up to the walls facing the other. Here the 18 ft wall equals the 11 ft and 7 ft walls opposite it, and the 14 ft wall equals the 9 ft and 5 ft walls. If they don't add up, a number is wrong.
A closet, a bay or the nook beside a fireplace is a small room in itself: measure its width and depth, and note where its opening sits along the main wall.
Measure an angled wall's length and locate both of its ends from the nearest corners. For a curved bay, measure the width of the opening and how far the curve projects at its centre.
The square footage of a room is its length multiplied by its width, both in feet. For an L-shaped room, add up its rectangles; subtracting the missing corner from the full rectangle gives the same answer, which makes a handy check.
Turn inches into decimal feet first by dividing by 12: 12 ft 6 in is 12.5 ft, not 12.6 ft, and 6 ft 9 in is 6.75 ft.
| Room | Working | Square feet | Square metres |
|---|---|---|---|
| A 12 by 12 ft room | 12 × 12 | 144 | 13.4 |
| A 10 by 12 ft room | 10 × 12 | 120 | 11.1 |
| A 20 by 20 ft room | 20 × 20 | 400 | 37.2 |
| The example bedroom | 12.5 × 15 | 187.5 | 17.4 |
| The L-shaped room, in rectangles | 18 × 9 + 11 × 5 | 217 | 20.2 |
| The L-shaped room, by subtraction | 18 × 14 − 7 × 5 | 217 | 20.2 |
Buying flooring? Work from the larger reading of each wall and add the waste allowance your supplier recommends, commonly 5 to 15 percent. That allowance is for the order, never for the plan.
Measure both diagonals. A room whose opposite walls match and whose diagonals match is a rectangle, so you can draw it with square corners. Few rooms are perfect, so the real question is whether the difference is bigger than your measuring error.
| What you measure | What it means | How to draw it |
|---|---|---|
| Opposite walls match, and the diagonals are within ½ in (1 cm) | The room is square. Treat a difference this small as measuring error rather than a crooked room. | With square corners |
| Opposite walls match, but the diagonals differ by more | The room is skewed: every corner is out of square by the same amount. In a room up to about 1½ times as long as it is wide, each wall's far end is out by less than the diagonals differ; in a longer, narrower room, the long walls can be out by more. | Square for a furniture layout; with the real angle where cabinets, countertops or flooring run along those walls |
| Opposite walls don't match | At least one wall isn't parallel to the wall across from it. | From triangles: two walls that meet at a corner, plus the diagonal between their far ends, fix that corner |
The same 12 ft 6 in by 15 ft bedroom, but the diagonals read 19 ft 5½ in and 19 ft 7 in: 1½ in apart. Worked through, the far end of each 15 ft wall is about 1⅛ in out of square, and the far end of each 12 ft 6 in wall about 1 in. A bed won't notice. A run of wall cabinets will. The longer diagonal runs between the two corners that are tighter than 90°.
Mark 3 ft along one wall from the corner and 4 ft along the other. If the corner is square, the two marks are exactly 5 ft apart. Double it to 6, 8 and 10 ft for a more reliable check, or use 60, 80 and 100 cm.
Wall lengths alone don't fix a room's shape: the same four walls can lean. Each diagonal closes off a triangle, and three sides fix a triangle, so a room with n walls needs n − 3 diagonals: 1 for a four-walled room, 3 for an L-shaped one. Measure one more as a check.
It depends on what they are for, and so does which number you write down when a wall measures differently at each end.
| Measuring for | Round to | If a wall reads differently at each end |
|---|---|---|
| A floor plan or layout sketch | ¼ in (5 mm) | Write both. Draw the average, or the angle if they differ by more than ½ in |
| Furniture that has to fit | ¼ in (5 mm) | Use the smaller reading: the tightest point decides whether it fits |
| Flooring, tiles or paint | ½ in (1 cm) | Use the larger reading, then add your supplier's waste allowance |
| Built-in cabinets or countertops | 1/16 in (2 mm) | Record both ends and both diagonals. The installer will measure again, but needs to know the wall is out |
| A home's square footage (US) | 1 in, or a tenth of a foot | Measure the outside of the exterior walls, as the ANSI Z765 standard used by appraisers does |
Yes. Two pages: a blank sheet with a grid sketch area, a table for the walls, boxes for the checks and a description to fill in, and the same sheet filled in for the bedroom used throughout this guide.
Print one sheet per room, and photograph each finished sheet before you leave the room.
Short answers to the questions that come up most.
Write the numbers down wall by wall, in a fixed order: the room's size, then each wall and what is on it, then what can't move. A designer, a contractor or an AI generator reads the same notes the same way.
| Wall | Length | Readings from its left-hand corner | What's on it |
|---|---|---|---|
| A | 12′ 6″ | 0 · 2′ 0″ · 4′ 10″ · 12′ 6″ | Door frame 2′ 0″ to 4′ 10″, opens in, hinges at 2′ 0″ |
| B | 15′ 0″ | 0 · 15′ 0″ | Nothing |
| C | 12′ 6″ | 0 · 3′ 9″ · 8′ 9″ · 12′ 6″ | Window frame 3′ 9″ to 8′ 9″ |
| D | 15′ 0″ | 0 · 15′ 0″ | Nothing |
| Diagonals | 19′ 6¼″ and 19′ 6¼″: square | ||
| Ceiling | 8′ 0″ | ||
Bedroom, 12 ft 6 in wide by 15 ft deep, ceiling 8 ft, square corners. Door on the bottom wall, 2 ft 10 in wide, starting 2 ft from the right-hand corner, hinged on that side and opening into the room. Window on the top wall, 5 ft wide, centred. Keep the door and the window where they are. It needs to fit a queen bed, a dresser and a desk.
Length and width get swapped between the person measuring and the person drawing. Say which wall a figure runs along: by compass direction if you know where north is, otherwise top, right, bottom and left as your sketch is drawn.
For each door and window, give the wall, the width and how far it starts from a named corner, and for doors which way they open. Sizes set the proportions; the openings decide where the furniture can go.
Feet and inches or metres, not both. Mixed units are the quickest way to get a drawing that is scaled to neither.
The door, a window, a radiator, a plumbing stack, a fireplace. Anything you don't pin down is open to a different layout.
List the rooms in the order you walk through them, say which door joins which rooms, and give the outside size of the floor if you measured it.
Type a description like this into the AI floor plan generator
Or photograph the measured sketch and use sketch to floor plan
Type in the room sizes and where the doors and windows are, or upload your measured sketch, and get a clean floor plan back as a PNG.
