Geometry calculators give you fast, formula-driven answers for a wide range of shapes and solids. Whether you need the Circle Area Calculator, the Ellipse Circumference Calculator, the Cylinder Volume Calculator, or the Pyramid Volume Calculator, every tool here applies standard geometric formulas so students, designers, and engineers get reliable results without the manual algebra.
Browse the Popular list to see which tools other users reach for most, or switch to the Trending tab to catch what's gaining traction right now. Every calculator on this page is completely free, needs no account, and works on any phone, tablet, or desktop.
- Volume Calculator
- Area Calculator
- Perimeter Calculator
- Surface Area Calculator
- Circle Calculator
- Rectangle Calculator
- Triangle Calculator
-
Triangle Area Calculator Without HeightFind the area of a triangle without knowing its height. Enter the three side lengths and this Heron formula calculator returns the exact area.
-
Complete the Square to Find Circle Center & RadiusConvert the general circle equation x²+y²+Dx+Ey+F=0 to standard form. Instantly find the center (−D/2, −E/2) and radius by completing the square.
-
Acre-Feet to Gallons CalculatorConvert acre-feet to US gallons instantly. Enter acre-feet and get the exact gallon volume using 1 acre-foot = 325,851 gallons.
-
Scale Factor CalculatorFind the scale factor (k) of a dilation from original and new dimensions, plus the area ratio (k²) and volume ratio (k³). Free, instant, and easy.
-
Arc Length Calculator (s = rθ)Calculate the arc length of a circle from its radius and central angle using s = rθ. Supports angles in radians or degrees, with instant results.
-
Volume of a Prism CalculatorCalculate the volume of any prism instantly using base area times height (V = B × h). Free, accurate calculator for triangular, rectangular and polygonal prisms.
-
Exterior Angle of a Polygon CalculatorFind each exterior angle, interior angle, and angle sums of any regular polygon. Enter the number of sides to compute 360/n instantly.
-
Distance from a Point to a Line CalculatorFind the perpendicular distance from a point (x₀, y₀) to a line a·x + b·y + c = 0 in 2D. Instant, exact results with worked steps.
-
Sum of Interior Angles of a Polygon CalculatorCalculate the sum of interior angles of any polygon using (n − 2) × 180. Enter the number of sides to get the total and each angle for a regular polygon.
-
Rectangle Pixel Dimensions from Print Size and DPI CalculatorCalculate the pixel width and height a rectangular image needs for a given print size and DPI. Get total pixels and megapixels instantly.
-
Air Volume of a Rectangular Room CalculatorCalculate the air volume of a rectangular room in cubic metres from its length, width and height. Free, instant, and great for HVAC and ventilation sizing.
-
Rectangle Height from Width and Aspect RatioFind a rectangle's height from its width and aspect ratio. Enter width and ratio (e.g. 16:9) to get the proportional height instantly.
-
Rectangle Print Size from Pixels and DPI CalculatorCalculate the printed width and height of a rectangular image from its pixel dimensions and DPI. Get results in inches and centimeters instantly.
-
Rectangular Roof Area CalculatorCalculate the actual sloped surface area of a rectangular roof from its footprint length, width, and pitch angle. Get square feet and roofing squares.
-
Rectangular Raised Garden Bed Soil CalculatorCalculate how much soil to fill a rectangular raised garden bed. Enter length, width and depth to get cubic feet, cubic yards, bags and liters.
-
Fence Posts for a Rectangular Yard CalculatorEstimate how many fence posts you need for a rectangular yard. Enter length, width, and post spacing to get the total posts, corners included.
-
Rectangular Tablecloth Size CalculatorCalculate the right rectangular tablecloth size from your table length, width and desired drop. Get exact cloth dimensions in inches instantly.
-
Square Feet to Square Yards for a Rectangle CalculatorConvert a rectangle's dimensions in feet to square yards instantly. Enter length and width in feet to get the area in square yards (1 sq yd = 9 sq ft).
-
Angle Between Two Lines CalculatorFind the acute angle between two straight lines from their slopes m₁ and m₂ using θ = arctan(|(m₁−m₂)/(1+m₁m₂)|). Get the result in degrees and radians.
-
Section Modulus of a Rectangular Beam CalculatorCalculate the elastic section modulus S = b·h²/6 of a rectangular beam cross-section, plus moment of inertia and area. Fast, accurate engineering tool.
-
Rectangle Width from Height and Aspect Ratio CalculatorFind a rectangle's width from its height and aspect ratio. Enter height and a ratio like 16:9 to instantly get the matching width. Free online tool.
-
Triangle Classification by Sides CalculatorClassify a triangle as equilateral, isosceles, or scalene from its three side lengths. Free instant calculator with a built-in valid-triangle check.
-
Rectangular Field / Plot Area CalculatorCalculate the area of a rectangular field or plot of land from its length and width in meters, feet, or yards. Get results in m², hectares, and acres.
-
Circumference to Diameter CalculatorConvert a circle's circumference to its diameter instantly with d = C / π. Free online calculator that also gives the radius. Works with any unit.
Frequently asked questions
What kinds of shapes and measurements can I calculate here?
The collection covers 2-D shapes such as circles, ellipses, rectangles, and heptagons, as well as 3-D solids including cylinders and pyramids. You can find areas, volumes, circumferences, and derived angles — useful for everything from math homework to layout planning and material estimation.
How accurate are the geometry results?
All tools use standard geometric formulas — for example, πr² for circle area and ⅓Bh for pyramid volume — tested against textbook references. Results are mathematically precise within normal floating-point limits. For safety- or construction-critical work, always verify dimensions against the governing engineering standard and have a qualified engineer review your figures.
Is there a cost or sign-up required?
No. Every calculator on CalculatorLib is free to use with no account, email address, or subscription needed. Open any tool and start calculating right away.
Does the site save or store the numbers I enter?
No. All calculations run entirely in your browser. No input data is transmitted to our servers or stored anywhere — your figures stay on your device.
How do I find the most popular geometry calculators?
The default category listing is ordered by real-world usage, so the most frequently used tools appear first. You can also open the Trending and Recently Added tabs at the top of the category page to explore what other users are discovering.
