Use this free room size calculator to plan a home-improvement or DIY project from the measurements and product information you already have.
HomeCalc shows the formula behind the result and keeps product-dependent assumptions editable where possible, so the calculation can match the material, package or supplier you actually plan to use.
For a rectangular room, floor and ceiling area are length × width, while perimeter is twice the sum of length and width. HomeCalc shows both area and perimeter so the same measurements can support flooring, paint, trim and layout planning.
FREE ROOM SIZE CALCULATOR
Room Size Calculator: Square Feet, Area & Perimeter
Calculate room area, perimeter and ceiling area from length and width.
Estimated result
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Get the room area and perimeter from two measurements
For a rectangular room, floor and ceiling area are length × width, while perimeter is twice the sum of length and width. HomeCalc shows both area and perimeter so the same measurements can support flooring, paint, trim and layout planning.
length × width = room area
What to check before using the result
- Measure finished wall-to-wall dimensions for floor planning.
- Split L-shaped or irregular rooms into rectangles and add their areas.
- Use perimeter rather than area when estimating linear materials such as some trim products.
- Ceiling area normally matches floor area in a simple rectangular room.
Area tells you how much surface there is, while perimeter tells you the distance around it. Flooring uses area; many trim and edge materials use linear length.