Free Geometry & Construction Calculators
35 free geometry calculators covering triangles, circles, polygons, area, volume, surface area and coordinate geometry — plus practical construction estimators for concrete, tile, paint, flooring, roofing and more. Every tool runs in your browser and explains the formula it uses.
About geometry calculators
Geometry calculators turn measurements into useful answers — the area of a strangely-shaped room, the volume of a cylindrical tank, the amount of concrete needed for a foundation, or the number of tiles required for a bathroom floor. This section collects the shape solvers and construction estimators people actually use, each with its own dedicated page, formula explanation and worked example.
If you want to understand the maths before using a tool, start with our guide on calculating square footage. For construction quantities, the concrete calculator and square footage calculator are the two most-used tools on the site.
2D Shapes & Planar Geometry
Triangles, quadrilaterals, circles and polygons — area, perimeter, sides and angles.
Triangle Calculator
Solve triangle sides, angles, area and perimeter from partial input.
Right Triangle Calculator
Solve right-triangle sides, angles and area from partial input.
Pythagorean Theorem Calculator
Find the missing side of a right triangle using a² + b² = c².
Circle Calculator
Compute radius, diameter, circumference and area from any single value.
Rectangle Calculator
Compute rectangle area, perimeter and diagonal.
Square Calculator
Calculate square area, perimeter and diagonal.
Polygon Calculator
Compute polygon area, perimeter and interior angles.
Trapezoid Calculator
Find trapezoid area, perimeter and height.
Parallelogram Calculator
Compute parallelogram area and perimeter from base, side and height.
Rhombus Calculator
Calculate rhombus area, perimeter and diagonals.
Ellipse Calculator
Compute ellipse area, circumference and eccentricity.
Sector Area Calculator
Compute sector area and arc length from radius and angle.
Arc Length Calculator
Find the length of an arc from radius and central angle.
Angle Converter
Convert between degrees, radians, gradians and turns.
Degrees & Radians Converter
Convert angles between degrees and radians.
Coordinate Geometry Calculator
Solve slope, distance, midpoint and line equations from two points.
3D Solids — Volume & Surface Area
Volume and surface area for spheres, cylinders, cones, prisms and pyramids.
Volume Calculator
Compute volume for cubes, spheres, cylinders, cones and prisms.
Surface Area Calculator
Find total surface area for common 3D shapes.
Sphere Calculator
Compute sphere radius, diameter, surface area and volume.
Cylinder Calculator
Calculate cylinder volume and surface area.
Cone Calculator
Compute cone volume, slant height and surface area.
Pyramid Calculator
Find pyramid volume, base area and lateral surface.
Cube Calculator
Compute cube volume, surface area and diagonal.
Rectangular Prism Calculator
Find volume, surface area and diagonal of a rectangular prism.
Construction & Home Project Estimators
Material quantity estimators for concrete, flooring, painting, roofing and more.
Concrete Calculator
Estimate concrete volume, bags and cost for slabs, footings and columns.
Square Footage Calculator
Calculate square footage for rooms, floors and irregular spaces.
Flooring Calculator
Estimate flooring quantity and cost with waste allowance.
Tile Calculator
Estimate the number of tiles, boxes and adhesive needed for an area.
Paint Calculator
Estimate paint quantity and cost based on wall area and coats.
Mulch Calculator
Estimate mulch volume and bags for garden beds.
Gravel Calculator
Estimate gravel volume, weight and bags or truckloads.
Roofing Calculator
Estimate roofing squares, shingles and underlayment from roof dimensions.
Stair Calculator
Calculate riser height, tread depth and number of steps.
Wall Area Calculator
Calculate wall area with deductions for doors and windows.
Fence Calculator
Estimate posts, rails, pickets and concrete for fence projects.
Geometry & Construction Guides
Learn the formulas behind the tools before you use them.
Geometry Calculator FAQs
No. You need enough information to determine the triangle uniquely — typically three of its sides or angles, with at least one side included. Combinations include SSS, SAS, ASA and AAS.
Break the room into simple shapes (rectangles, triangles) that you can measure separately, calculate the area of each, and add the results. The square footage calculator supports multiple sections.
Use the concrete calculator — it converts slab dimensions into volume, then into the number of 40 lb, 60 lb or 80 lb bags, plus cubic yards if you are ordering a ready-mix delivery.
They are useful for budgeting and material ordering. Always add a waste allowance (typically 5–10%) and verify critical quantities with your supplier or contractor. Local codes and site conditions may require additional material.
Explore Other Categories
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