Rectangular prism
8 x 5 x 3158 square units
Surface Area Calculator
Use this free surface area calculator to find outside area for boxes, cubes, cylinders, spheres, and cones with formulas, square-unit notes, and copyable steps.
Unit-aware inputsFormula noteExample numbersTab-only history
SA = 2lw + 2lh + 2wh158 cm^2
- Length
- 8 cm
- Width
- 5 cm
- Height
- 3 cm
Steps
- Choose rectangular prism mode.
- Use SA = 2lw + 2lh + 2wh.
- Substitute the entered measurements.
- The surface area is 158 cm^2.
Recent answers
Recent surface area answers will appear here.
Privacy note
Geometry answers and history stay in this browser tab while you work.
Copy answer only writes the current result to your clipboard when you press it.
How to use the Surface Area Calculator
- Choose the solid shape: rectangular prism, cube, cylinder, sphere, or cone.
- Enter the required measurements for that shape.
- Press Calculate surface area to see the square-unit result and formula steps.
- Use examples, recent answers, or copy the result while checking geometry work.
What people use it for
Find the outside area before wrapping, painting, or covering a simple solid.
Compare formulas for rectangular prisms, cubes, cylinders, spheres, and cones.
Check square-unit answers for geometry homework.
Estimate material coverage for boxes, cans, balls, and cones before adding waste or overlap.
Keep surface area separate from volume and capacity problems.
Copy formula steps and recent answers into notes while comparing shapes.
Quick examples
Cube
s=6216 square units
Sphere
r=4201.06192983 square units
Cylinder
r=3, h=10245.04422698 square units
Cone
r=3, h=475.39822369 square units
Painted box check
12 x 8 x 6 in432 in^2 before waste
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Surface Area CalculatorSee slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- CalculatorsBrowse related calculators and utilities in the same category.
- Calculator and utility guidesFind more guides that use real tool inputs and example numbers.
- All free toolsSearch every live tool, converter, calculator, AI helper, and browser utility.
Frequently asked questions
Quick answers about formulas, units, valid measurements, examples, copying, and private in-browser history.
Which shapes are supported?
The Surface Area Calculator supports rectangular prism, cube, cylinder, sphere, and cone modes.
Which measurements do I need for each shape?
Rectangular prisms need length, width, and height. Cubes need side length. Cylinders and cones need radius and height. Spheres need radius.
What do the main Surface Area Calculator inputs mean?
The main inputs are the numbers, operation, mode, or known values the calculator needs. Keep units consistent, enter percentages the way the page label shows, and use the examples as a quick check before trusting the answer.
How should I read the Surface Area Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the Surface Area Calculator?
Check units, signs, rounding, and the selected mode before copying the answer. If the number feels weird, rerun one of the examples first, then put your own values back in slowly.
Should I enter radius or diameter?
Enter radius for cylinders, spheres, and cones. If you only know diameter, divide it by 2 first so the surface area is not four times too large.
What units should I use?
Use the same length unit for every measurement. The result is reported in square units, such as cm^2 or ft^2.
Which formulas does the calculator use?
It uses 2lw + 2lh + 2wh for boxes, 6s^2 for cubes, 2pi r^2 + 2pi rh for cylinders, 4pi r^2 for spheres, and pi r(r + l) for cones.
How does cone surface area work?
Cone surface area uses pi r(r + l). This calculator finds slant height l from radius and vertical height using the Pythagorean theorem.
What is the difference between surface area and volume?
Surface area measures the outside of a solid in square units. Volume measures the space inside a solid in cubic units.
Can this calculate flat 2D shapes?
Use the Area Calculator for flat shapes such as rectangles, triangles, circles, trapezoids, and parallelograms.
Can I use this for paint, wrap, or material estimates?
Yes for a first closed-shape estimate, but add extra for waste, seams, overlap, texture, openings, and real object details the formula does not include.
Does it handle open-top boxes or missing faces?
No. The built-in modes calculate closed standard solids. For an open-top box, subtract the missing face area from the rectangular prism result.
Is my surface area history private?
Yes. Recent surface area answers stay only in the current browser tab while you use the page. They are not sent to a server.