Square Footage Calculator
Add as many rooms or lot sections as you need — mix rectangles, triangles, and circles, in feet/inches or metric — and get one running total in ft², m², and yd². Everything recalculates instantly, and nothing you type leaves your browser.
Formula used: rectangle = length × width; triangle = ½ × base × height; circle = π × radius². Each section's area is converted to feet before being added to the running total.
A 14 ft × 12 ft bedroom (rectangle) plus a 6 ft × 5 ft closet (rectangle):
Bedroom: 14 × 12 = 168 ft²
Closet: 6 × 5 = 30 ft²
Total: 168 + 30 = 198 ft²
= 198 / 10.7639 ≈ 18.40 m²
= 198 / 9 ≈ 22.0 yd²
At $4.50/ft²: 198 × 4.50 = $891.00 How to use this calculator
- Pick a shape for the first area — rectangle, triangle, or circle — and choose feet/inches or metric.
- Enter the dimensions. For feet/inches, the inches field only needs a value between 0 and 11.99.
- Click "Add another room or area" for each additional space, and remove any you don't need.
- Optionally enter a cost per square foot to see an estimated total cost.
- Use "Copy result" to copy a plain-text summary, or "Reset" to start over.
How the calculation works
Every shape is converted to square feet before the sections are added together, so you can freely mix a metric bedroom with an imperial closet in the same total. Rectangles multiply length by width; triangles use half the base times the height; circles use π times the radius squared. A negative, zero, or empty dimension is flagged as an error for that field rather than silently producing a wrong total, and the running total is only shown once every section is valid.
FAQ
Does this account for wall thickness?
No — it measures the shape you enter. If you want interior floor area, measure inside the walls; if you want a footprint or lot area, measure to the outer edge.
I only know the diameter, not the radius — what do I enter?
Divide the diameter by two before entering it as the radius. A 10 ft diameter round room uses a 5 ft radius.
Can I mix feet/inches sections with metric sections?
Yes — each section has its own unit toggle, and every section is converted to square feet internally before the totals are added.