Built by Russell Whitton
Russell is a structural drafter and structural designer with more than 25 years of experience producing and interpreting technical drawings across structural and infrastructure projects.
Why I built Draw to Scale →Geometry, drawn to scale
Free geometry calculators
Clean, accurate tools for everyday geometry. Enter what you know, get every value back instantly — and see the shape drawn properly, with dimensions you can click to edit.
2D shape calculators
Triangle Solver
Solve any triangle from any three values — SSS, SAS, ASA, AAS and the ambiguous SSA case — with area, angles, medians and more.
Open tool →Circle Calculator
Enter any one of radius, diameter, circumference or area and the other three appear at once, with the circle drawn and dimensioned.
Open tool →Circle Sector & Arc
Arc length, sector area, chord and segment from a radius and angle — or any two values. The slice is drawn true to scale.
Open tool →Annulus (Ring)
The flat ring between two circles — washer, gasket or track. Ring area, both circumferences and the width from the two radii, drawn to scale.
Open tool →Circular Segment
The region a chord cuts off a circle — flats, arches and part-full pipes. Any two of radius, angle, chord and height solve the rest, drawn to scale.
Open tool →Ellipse
Area, circumference, eccentricity and foci from the two semi-axes — with the curve drawn true to scale.
Open tool →Right Triangle & Pythagoras
Find the legs, hypotenuse and angles from any two values, with a live a² + b² = c² readout for the Pythagorean theorem.
Open tool →Rectangle & Square
Area, perimeter and diagonal from any two of length, width, diagonal, area or perimeter — squares included.
Open tool →Trapezoid
Area and median from the two parallel bases and the height, plus perimeter when you add the legs.
Open tool →Regular Polygon
Side, area, perimeter, circumradius, apothem and the interior and exterior angles for any regular polygon.
Open tool →Parallelogram & Rhombus
Area, height, perimeter and both diagonals from two sides and the angle — rhombus, rectangle and square detected.
Open tool →ADVERTISEMENT · 728 × 90
3D volume calculators
Volume hub →Cube
Volume, surface area and the face and space diagonals from a single side length — drawn as an isometric figure you can edit.
Open tool →Rectangular Prism
The classic box: length × width × height gives volume, with surface area and the space diagonal alongside.
Open tool →Cylinder
Volume, lateral area and total surface area from radius and height — tanks, drums, posts and pipes that run full.
Open tool →Pipe
A hollow cylinder — the volume of the wall material itself from outer and inner diameters, not the bore.
Open tool →Capsule
A cylinder with hemispherical ends — pressure vessels, tanks and pills. Volume and surface from radius and length.
Open tool →Cone
Volume, slant height, lateral and total surface area from the base radius and height — hoppers, funnels and stockpiles.
Open tool →Sphere
The four-thirds rule from a single radius — volume, surface area and great-circle values, drawn to scale.
Open tool →Square Pyramid
A square base rising to an apex — volume, slant heights and face areas from base side and height.
Open tool →Frustum
A cone with the top cut off — buckets, lampshades and tapered tanks. Volume and surfaces from the two radii and height.
Open tool →Triangular Prism
A triangle swept along a length — ramps, roof volumes and wedges. Volume and surface area from the cross-section.
Open tool →Hemisphere
Half a sphere — a dome plus its flat base. Volume, curved surface and total surface from one radius.
Open tool →Spherical Cap
A dome sliced from a sphere — dished tank ends and domes. Volume and curved surface from base radius and rise.
Open tool →Ellipsoid
A sphere stretched along three axes — eggs, rugby balls and squashed spheres. Volume from the three semi-axes.
Open tool →Torus
A ring or doughnut shape — o-rings, tyres and ring beams. Volume and surface area from the two radii.
Open tool →Polygon Prism
A regular prism with any number of sides — pentagonal, hexagonal, octagonal and beyond, from side length and height.
Open tool →Tank Fill Level
How much is in a horizontal tank that's only partly full? Diameter, length and dipstick depth give litres, percentage full and capacity — drawn to scale.
Open tool →Accurate
Real trigonometry and geometry under the hood — the same maths you'd do by hand, checked.
Drawn to scale
Every answer comes with a clean dimensioned figure — and you can click a value to change it.
Free & instant
No sign-up, no waiting. Works on your phone, in class, or on the job site.
About these calculators
Draw to Scale is a small, growing collection of calculators for the shapes people look up most. Each one is built to do a single job well: take the values you have, return every value you don't, and show the result as a proper drawing rather than a wall of numbers.
They're aimed at students, teachers, makers, tradespeople and anyone who needs a quick, trustworthy answer. The collection now spans 2D shapes and a full set of 3D volume calculators — cubes, cylinders, spheres, cones, pyramids and more — with further tools on the way.