Area Calculator
Updating live using standard Euclidean geometry formulas (A = πr² for a circle, A = lw for a rectangle). Related: square footage, volume.
Show the math
What your result means
- Area is how much 2D space the shape covers. The unit is whatever you entered, squared — inches in, square inches out; meters in, square meters out.
- Perimeter is the distance around the outside. Use it when you need to buy edging, framing, fencing, or trim that wraps the shape.
- Every formula here is standard Euclidean geometry, the same math used in K–12 textbooks and professional CAD tools. The ellipse perimeter uses π(a+b) — a simple approximation that stays within a few percent for landscaping and craft uses.
- Try switching between shapes with the same dimension to see how much area you gain by rounding a rectangle into an ellipse, or how perimeter grows as a square stretches into a long rectangle.
Quick questions
What units should I enter?
Any unit — just stay consistent. Enter inches and your area comes back in square inches; enter meters and it comes back in square meters. The calculator is unit-agnostic.
Why isn't my triangle perimeter updating?
Base and height alone are enough to compute area, but perimeter needs all three sides (a, b, c). Fill in the three side fields to see the perimeter.
How accurate is the ellipse perimeter?
We use π(a+b), a simple approximation. For landscaping, crafts, and most real-world work it's within a few percent of the true value. Exact ellipse perimeter requires an elliptic integral.
Reviewed by the FriendlyCalc Math & Editorial Team. Last reviewed: 2026-04 · Last methodology update: 2026-04 · Next review due: 2027-04
Method & review
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.