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Surface Area Calculator

Select the shape you want to analyze and enter only the inputs that apply to that shape. Leave other fields blank.

All dimensions must be positive numbers. Use the 'Units' box to label your result (e.g., cm, m, in); calculations are unit-agnostic.

Tips: For cones, enter the vertical height; the calculator computes slant height automatically. For triangular prisms, ensure the triangle sides satisfy the triangle inequality (a + b > c, etc.).

Use our Surface Area Calculator to quickly find the total exterior area of common 3D shapes, including cubes, rectangular prisms, spheres, cylinders, cones, and triangular prisms. Enter your dimensions, choose your shape, and get instant results with the essential formulas and tips.

What is surface area?

Surface area is the total area that covers the outside of a three-dimensional object. It is measured in square units (such as cm2, m2, or in2) and is crucial for tasks like painting, wrapping, coating, 3D printing, and materials estimation. Knowing how to calculate surface area ensures you buy the right amount of material and plan accurately.

Shapes supported by the Surface Area Calculator

  • Cube: A box with equal edges. Formula: 6s2.
  • Rectangular prism: A box with length, width, and height. Formula: 2(lw + lh + wh).
  • Sphere: A perfectly round ball. Formula: 4?r2.
  • Cylinder: A circular tube. Formula: 2?r(r + h).
  • Cone: A shape that tapers to a point. Total surface area uses slant height s: ?r(r + s), where s = ?(r2 + h2).
  • Triangular prism: A prism with triangular ends. Formula: (perimeter of base) × L + 2 × area of triangle. Triangle area via Heron’s formula.

How to use the calculator

  1. Select your shape from the dropdown.
  2. Enter only the dimensions relevant to that shape (for example, radius and height for a cylinder). Leave the rest blank.
  3. Optionally add a unit label (cm, m, in) for clearer results.
  4. Choose the number of decimal places.
  5. Click Calculate to see the surface area instantly.

Formulas used by the calculator

  • Cube: SA = 6s2
  • Rectangular prism: SA = 2(lw + lh + wh)
  • Sphere: SA = 4?r2
  • Cylinder: SA = 2?r(r + h)
  • Cone: SA = ?r(r + ?(r2 + h2))
  • Triangular prism: SA = (a + b + c)L + 2 × ?(s(s ? a)(s ? b)(s ? c)), where s = (a + b + c)/2

Practical examples

Planning to paint a storage box? Use the rectangular prism option to compute the total area to be painted. Wrapping a gift shaped like a cube? The cube formula gives you the precise paper area needed. Estimating material for a cylindrical tank? Enter its radius and height to get an accurate coating area. For conical funnels, the calculator determines slant height internally from the given height. For triangular ducting, the triangular prism option accounts for both the side faces and the two triangular ends.

Tips for accurate results

  • Keep units consistent across all inputs (all in cm or all in inches).
  • Measure to the nearest practical increment, then choose suitable decimal places in the calculator.
  • For triangular prisms, ensure the three sides can form a triangle (a + b > c, a + c > b, b + c > a).
  • When estimating paint or wrap, add an extra margin for overlaps, waste, or texture.

Why this Surface Area Calculator stands out

This calculator is designed to be fast, accurate, and easy to use. It supports the most common 3D shapes, provides plain-language guidance, and formats results with your chosen precision and unit label. Whether you’re a student checking homework, a DIYer planning materials, or a professional preparing estimates, you can rely on this tool for consistent, formula-driven answers.

FAQs

How do I use the Surface Area Calculator for a cylinder?

Select cylinder, enter radius and height, choose decimals and units, then calculate to get 2?r(r + h).

Which shapes are supported by the Surface Area Calculator?

Cube, rectangular prism, sphere, cylinder, cone, and triangular prism are included.

Does the Surface Area Calculator handle cone slant height?

Yes. Enter the cone’s radius and vertical height; the calculator computes slant height automatically.

Can I add units in the Surface Area Calculator?

Yes. Type any unit label, like cm or in; the result will display in those squared units.

What precision does the Surface Area Calculator use?

You choose decimal places from 0 to 10. The default is 2.

How does the Surface Area Calculator find triangular prism area?

It uses Heron’s formula for the triangle, then adds lateral area: (a+b+c)L + 2×area.

Is the Surface Area Calculator accurate for spheres?

Yes, it uses SA = 4?r² with high-precision ? and your selected decimal places.