Geometry Calculator
Calculate area, perimeter, circumference, surface area, volume, and other common geometry measurements for 2D and 3D shapes. Choose the shape and dimensions carefully, keep units consistent, and use the formula guide below when you need to show your work.
Geometry Calculator Tips
Geometry calculations depend on choosing the right shape, the right measurement, and the right units. Area measures flat space, perimeter and circumference measure distance around a shape, surface area measures the outside of a 3D solid, and volume measures the space inside it. Enter dimensions in the same unit whenever possible.
Quick Guide
- Choose the exact shape before entering dimensions.
- Decide whether you need area, perimeter, surface area, or volume.
- Use the same unit for all related measurements.
- Check the formula section when you need to show your work.
Shape Formulas
Calculate formulas for common 2D and 3D shapes with the dimensions you enter.
Area vs Perimeter
Separate inside space from distance around a shape so you choose the correct result.
Surface Area & Volume
Work with boxes, cylinders, cones, spheres, and other solids using consistent units.
Geometry Formula Reference
Geometry formulas depend on both the shape and the measurement you need. Area covers flat space, perimeter measures the distance around a 2D shape, surface area measures the outside of a 3D solid, and volume measures the space inside a solid.
| Shape | Common Formula | Use It For |
|---|---|---|
| Rectangle | Area = length × width | Rooms, lots, screens, panels |
| Triangle | Area = base × height ÷ 2 | Roofs, ramps, diagrams |
| Circle | Area = πr²; Circumference = 2πr | Round spaces and circular paths |
| Box | Volume = length × width × height | Storage, shipping, containers |
| Cylinder | Volume = πr²h | Tanks, cans, pipes |
| Sphere | Volume = 4/3πr³ | Balls and round objects |
Area, Perimeter, Surface Area, and Volume
Area and perimeter are not the same. Area tells how much flat space is inside a shape, while perimeter tells the distance around it. Surface area and volume apply to 3D shapes: surface area measures the outside, and volume measures capacity or space inside.
Worked Geometry Examples
A rectangle that is 12 feet long and 10 feet wide has an area of 120 square feet. A circle with radius 5 has an area of about 78.54 square units. A box that is 4 by 3 by 2 has a volume of 24 cubic units.
Common Geometry Mistakes
- Mixing inches, feet, meters, or centimeters in the same calculation.
- Using diameter where the formula requires radius.
- Confusing square units with cubic units.
- Choosing perimeter when the project needs area.
- Rounding π too early in a multi-step problem.
Practical Uses for Geometry Calculations
Geometry calculators are useful for schoolwork, home projects, flooring, paint estimates, garden beds, storage boxes, shipping dimensions, crafts, construction layouts, and checking formulas before doing manual work.
Geometry Calculator FAQs
What is the difference between area and perimeter?
Area measures the space inside a 2D shape. Perimeter measures the distance around it.
What is the difference between surface area and volume?
Surface area measures the outside of a 3D object. Volume measures the space inside it.
Should I use radius or diameter for a circle?
Most circle formulas use radius. Radius is half the diameter.
Why do units matter in geometry?
Using different units in the same formula can produce incorrect answers unless you convert them first.
What units should area use?
Area uses square units such as square feet, square inches, or square meters.
What units should volume use?
Volume uses cubic units such as cubic feet, cubic inches, or cubic meters.