Area Calculator
Pick a 2D shape — circle, square, rectangle, triangle, trapezium, parallelogram, ellipse, regular polygon, rhombus, sector, annulus or kite — to open its dedicated area calculator. Enter dimensions in any unit and get the answer in any area unit, with the formula and worked example.
The Korvaix Area Calculator is a hub for our individual 2D shape area calculators. Pick the shape you need below to open its own dedicated page with the formula, worked example, and a clear breakdown of the result.
All shapes accept inputs in mm, cm, m, km, inches, feet, yards or miles — and you can mix units within a single calculation. Choose any area unit (mm², cm², m², km², in², ft², yd², mi², acres or hectares) for the answer.
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What this calculator does
A hub page that links to dedicated area calculators for 12 common 2D shapes — each with its own formula, worked example, and breakdown.
Who it is for
Students, teachers, DIYers, builders, decorators, fabricators, packaging designers, gardeners, anyone who needs to work out a flat area accurately and quickly.
How to use it
Pick a shape from the grid below. You will be taken to that shape's own calculator page where you can enter dimensions and get the area instantly.
How the calculation works
Each shape uses the standard area formula. Circle A=πr². Square A=a². Rectangle A=l×w. Triangle A=½·b·h. Trapezium A=½·(a+b)·h. Parallelogram A=b·h. Ellipse A=π·a·b. Regular n-gon A=¼·n·s²·cot(π/n). Rhombus and Kite A=½·p·q. Sector A=½·r²·θ (θ in radians). Annulus A=π·(R²−r²).
Worked example
A 6 m by 4 m room has floor area 6 × 4 = 24 m² (≈ 258 ft²).
Assumptions and limitations
- All shapes assume the standard, idealised flat geometric figure.
- Length unit conversions use exact SI/Imperial factors. Area conversions use the same factors squared.
- For trapezium, parallelogram and triangle, the 'height' field means perpendicular distance — not a slanted side.
Frequently asked questions
What is area?
Area is the amount of flat space inside a 2D shape, measured in square units (m², ft², in², cm² and so on).
What unit should I use for area?
Any unit that matches your inputs, but the calculator lets you mix units freely on input and pick any unit on output.
What's the difference between trapezium and trapezoid?
In UK English, a trapezium has one pair of parallel sides; in US English the same shape is a trapezoid. Both refer to the same 4-sided figure.
How do I find the area of a triangle if I only know the three sides?
Use Heron's formula: s = (a+b+c)/2; A = √(s·(s−a)·(s−b)·(s−c)). Our Triangular Prism Calculator includes Heron's formula.
Related calculators
- Annulus Area Calculator — Enter the outer and inner radii. The calculator returns A = π·(R² − r²).
- Capsule Surface Area Calculator — Enter the radius and the straight middle length. The calculator returns 4πr² for the two rounded ends plus 2πrh for the cylindrical side.
- Circle Area Calculator — Enter the radius. The calculator returns A = πr², the area of the flat disc.
- Circular Sector Area Calculator — Enter the radius and the angle in degrees. The calculator returns the sector's area: A = ½·r²·θ (with θ converted to radians).
- Cone Surface Area Calculator — Enter the base radius and height. The calculator splits the answer into the base (πr²) and the lateral surface (πr·s), where s = √(r²+h²) is
- Conical Frustum Surface Area Calculator — Enter the top radius, bottom radius and height. The calculator returns lateral area π(r₁+r₂)·s plus the two end discs.
Related guides
- Surface Area Formulas for Common 3D Shapes — A clear, plain-English guide to surface area formulas for sphere, cube, cone, cylinder, rectangular tank, capsule, spherical cap, conical frustum, ellipsoid and
Sources and references
Standard geometric area formulas (mathematics and engineering textbooks). SI and Imperial unit conversions per the International System of Units (SI) and NIST.
Last updated
Last reviewed: 2026-04-21.