Square Footage Calculator — Multiple Rooms & Cost

Rectangle or triangle rooms; totals in sq ft and m²; optional $/sq ft line.

Quick answer: Add up to 12 rooms with length, width and shape to get per-room and total square feet, square meters and an optional dollars-per-square-foot cost.

📏 Measure twice: tape along the floor at the longest points of each wall, and double-check closets and alcoves — the rooms that get skipped are the ones that blow up flooring orders.

How to use

  1. Add a row per room: label, length and width in feet.
  2. Switch odd-shaped rooms to triangle (½ × base × height).
  3. Add or remove rows up to 12, then press Total.
  4. Optional: enter a $/sq ft rate for an instant paint, flooring or reno budget.

About this tool

Square footage questions are rarely one rectangle — they are a bungalow of odd rooms, closets and that triangle corner nobody can measure cleanly. This calculator lets you build the space room by room: up to 12 labeled rows of length × width, each either rectangular or triangular (half base times height). You get per-room areas, the total in square feet and square meters, and an optional dollars-per-square-foot line that turns the total into a paint, flooring or renovation budget in one step. One honesty note for listings: real-estate square footage follows ANSI measurement rules taken from the home exterior, so your interior tape-measure total will not match the MLS number — by design. Nothing leaves your browser.

FAQ

How much does flooring cost per square foot installed?
Ballparks installed: carpet $3–$6, laminate $4–$8, luxury vinyl plank $4–$12, tile $8–$20 per sq ft. Materials-only typically runs 40–60% of those numbers. Multiply your room total from this calculator by the rate you were quoted for an instant sanity check.
How much paint do I need for a room?
One gallon covers roughly 350–400 sq ft of wall — and wall area is not floor area (it is wall perimeter × ceiling height, minus openings). Use the floor total here for flooring budgets, then estimate paint separately: a 12 × 12 room needs about 1.5–2 gallons for two coats of walls.
Is square footage measured inside or outside?
For real-estate listings, ANSI Z765 rules measure from the exterior of the home, which includes wall thickness, and exclude garages and below-grade basements. Interior tape-measure totals (like this one) will come out lower — that is expected, not an error.
Do closets count in square footage?
Finished, accessible closets inside the living area do count — both in interior measuring and under ANSI listing rules. Unfinished storage, crawl spaces and non-heated sunrooms do not. Label each closet as its own row here to keep the total honest.
How do I calculate a triangle room area?
Treat the longest wall as the base and measure perpendicular from it to the opposite corner as the height: area = ½ × base × height. Pick the triangle option on the row and enter base and height as L and W — the calculator applies the half factor for you.

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