Whether a piece of furniture works in a room comes down to two numbers, and neither is the room’s overall size. One is the largest rectangle that fits inside the space. The other is the narrowest opening on the route the piece travels to get there. This guide covers both.
Compared
| Polycam | Twindo | Tape and laser | |
|---|---|---|---|
| Room dimensions | Bounding box and inscribed, per room | Measure on device, free | Whatever you take |
| Openings on the route | Every door and window with width, height and area | Appears in the CAD as-built | One at a time |
| Existing furniture | Detected with width, height and depth | Not detected | Measure each piece |
| Deliverable | Spatial Report, floor plan, exports | CAD as-built in Revit, SketchUp, AutoCAD and others | Your notes |
| Cost | Business $400/yr per user | Free to scan and measure; as-builts from $0.14/sq ft | Free |
The Number You Need Is the Inscribed One
A Spatial Report gives two dimensions for every room, and the difference between them decides what fits.
Bounding box is the smallest rectangle that contains the room. Inscribed is the largest rectangle that fits inside it. In a rectangular room, they are nearly the same. In anything else, they are not, and the gap is where specification goes wrong.
The difference is largest in the rooms you would most want to get right. An L-shaped living room can report a bounding box eight feet longer than the rectangle that fits inside it. A hallway with a return can show a bounding width three times its usable width. If the order is larger than the first number, the piece will not fit.
Use the inscribed figure for anything that has to sit as a rectangle. A sofa, a bed, a rug, a dining table with chairs pulled out.
Use the bounding box for the envelope, when you need the extent of the room rather than what fits in it.
Use the floor plan itself for anything angled. Both figures assume a rectangle. An L-shaped room is better planned against the drawing.
The report gives floor area, perimeter, wall area and ceiling height per room alongside both dimension pairs. Ceiling height governs what can go on a wall and whether a tall piece reads as proportionate.
The Route Matters More Than the Room
Specifying a piece that cannot reach the room is the designer’s mistake rather than the client’s, and it is the one that costs a restocking fee.
Check every opening on the route, not just the room door. The report lists each door and window with a width, height and area. A single hallway will often carry four or five doors varying by six or eight inches between the widest and the narrowest. A piece has to clear the narrowest one on its path, and that is rarely the door you would have measured.
Work the route in order. Building entrance, lift or stair, landing, corridor, room door. Write down the narrowest dimension at each stage and specify against that.
Stairs and turns need more than a width. A turn needs diagonal clearance, which a plan shows and a single measurement does not. Capture the stair and the landing so the geometry is there when a supplier asks.
Check the door swing. A door that opens into the route reduces the clear width while it is open, so a 32 inch opening with a door in the way is narrower still.
Measure the piece across its diagonal. Most furniture passes through an opening at an angle, so the diagonal of the smallest face is the governing number rather than the width.
Planning Against What Is Already There
The report inventories the room’s contents, which removes the tedious half of a survey.
Each piece of furniture comes back with a width, height and depth, alongside fixtures and appliances. For a client keeping some pieces and replacing others, that inventory is the brief, and it arrives with the capture rather than costing an afternoon with a tape.
Verify anything you are designing around. Detection is a starting point rather than a survey. If a piece is staying and something new has to sit beside it, measure that one by hand.
For circulation, the standard clearances are set out in What to Use for Furniture Layout Planning.
Specifying What Is Not There Yet
Measurement ends where specification begins, and the same capture supports both.
The Floorplan Editor is where the layout gets tested. Reposition, resize or reorient the detected furniture, swap a piece for a library asset, and draw in a partition that does not exist. The plan, the 3D view and the report update together, so moving a sofa in plan moves it everywhere.
Object Mode captures a specific piece. An inherited chest, a showroom item, anything not in a library. Photogrammetry gives an editable mesh, and Gaussian splats give a photorealistic record. A single photograph carries no scale, so treat an AI Capture result as a look rather than a dimension.
Export for whoever needs it. Floor plans come out as PDF, DXF, PNG, SVG and CSV. The DXF suits anyone drawing over your survey.
The Spatial Report, the Floorplan Editor and floor plan downloads all sit on the Business plan at $400 a year per user. A 7-day trial covers running it against a live project.
For the capture itself, the room-by-room method is covered in How to Scan a House for Renovation Plans.
Where Twindo Fits
Twindo solves a narrower version of this, and solves it well.
Free on-device measurement. Scan on a LiDAR iPhone 12 Pro or newer, or an iPad Pro from 2020 or newer, and measure the result at no cost. If all you need is room dimensions, that is a free route and a real one.
Paid CAD as-builts. Their conversion service produces drawings in Revit, SketchUp, Chief Architect, Archicad, Vectorworks, 2020 Design Live and AutoCAD, priced per square foot and charged on delivery.
Rates depend on the tier. On the free Starter plan, a 2D floor plan is $0.18 per square foot, standard 3D CAD and BIM formats are $0.26, and select 3D formats with a measurement report are $0.29. Essentials at $29 a month drops those to $0.14, $0.22 and $0.25. Starter covers 2 projects a month and Essentials covers 5.
Their published rates apply to residential spaces up to 8,000 square feet. Anything larger is quoted.
It documents the shell. Twindo records the room rather than its contents, so there is no furniture inventory and no layout editor. For a designer working in SketchUp or Chief Architect, it puts an accurate room into that software. The missing half is what already sits in it.
Working out what actually fits?
FAQ
How do I measure a room for furniture layout?
Take the inscribed dimension rather than the overall one, since that is the largest rectangle fitting inside the room. Then measure every opening on the delivery route and use the narrowest. Record the dimensions of any furniture staying in the room.
What is the difference between bounding box and inscribed dimensions?
Bounding box is the smallest rectangle containing the room. Inscribed is the largest rectangle fitting inside it. They diverge in any room that is not rectangular, and the inscribed figure governs what fits.
How do I know if a sofa will fit through the door?
Check every opening on the route rather than just the room door, and use the narrowest. Measure the sofa across the diagonal of its smallest face, because most pieces pass through an opening at an angle.
Does a scan measure doors and windows?
Yes. A Spatial Report lists every detected opening with its width, height and area, per room, which makes delivery access checkable without walking the route with a tape.
Can I see what furniture is already in the room?
Detected furniture comes back with width, height and depth for each piece, alongside fixtures and appliances. Verify anything you are designing around, since detection is a starting point rather than a survey.
Which plan do I need?
Business, at $400 a year per user. The Spatial Report, the Floorplan Editor and floor plan downloads all sit there, and a 7-day trial covers a live project.
What does Twindo cost?
Scanning and on-device measurement are free. As-builts are priced per square foot: on the free Starter plan a 2D floor plan is $0.18, standard 3D CAD and BIM is $0.26, and select 3D with a measurement report is $0.29. Essentials at $29 a month lowers those to $0.14, $0.22 and $0.25. Published rates cover residential spaces up to 8,000 square feet.
