👆 Drag to Rotate • 📜 Scroll/Pinch to Zoom • Right-click to Pan
🛠️ Drawing Tools
📐 Classical Constructions
🔵 Conic Sections
📏 Measurement Calculator
Select two points, then click calculate:
🔺 Triangle Centers
Select a triangle to calculate centers:
📚 Learning Resources
✏️ Annotations
🔄 Transform
🖥️ Display Settings
⬡ Polygon Settings
Sides:6
0 shapes • 100% • 0, 0
💡 Tips: Shift+Click to multi-select • R to rotate • M to mirror
Space+Drag to pan • Scroll to zoom • Esc to cancel
3D ModeSelect Tool
🔋 100%Light
Keyboard Shortcuts
Undo
Ctrl + Z
Redo
Ctrl + Y
Select All
Ctrl + A
Deselect
Esc
Delete
Del
Zoom In
+
Zoom Out
-
Reset View
0
Copy
Ctrl + C
Paste
Ctrl + V
Pan Mode
Space + Drag
Tool Shortcuts
S/P/L/R/C/T/G
Arc / Ellipse
A / E
Spline / Text
B / X
Dim / Angle
D / N
Compass / Bezier
O / V
Perp Bisector / Angle Bisector
J / K
Parallel / Perpendicular
Q / W
Rotate 45°
R
Mirror Horizontal
Shift + M
Toggle Grid/Axes
G / F
Triangle Centers
Select a triangle and click "Calculate Centers"
📏 Measurement Calculator
Select two points, then calculate:
🎓 Geometry Tutorial
Getting Started
Welcome to the Calc84 Geometry Calculator! This tool provides classical compass and straightedge constructions along with modern geometric analysis.
Select Tool (S): Click and drag to select shapes
Point Tool (P): Place single points on the canvas
Line Tool (L): Draw straight lines
Compass Tool (O): Classical compass constructions
Classical Constructions
Use our Cabri Jr.-style tools for geometric constructions:
Perpendicular Bisector: Select two points to create the perpendicular bisector
Angle Bisector: Select vertex and two points on the angle rays
Parallel Line: Select a line, then a point to draw through
Perpendicular Line: Select a line, then a point for perpendicular
Triangle Centers
Create a triangle, then click "Calculate Centers" to discover:
Centroid (G): Intersection of medians
Circumcenter (O): Center of circumscribed circle
Incenter (I): Center of inscribed circle
Orthocenter (H): Intersection of altitudes
📚 Geometry Formula Reference
Coordinate Geometry
Distance Formulad = √[(x2-x1)² + (y2-y1)²]
Midpoint FormulaM = ((x1+x2)/2, (y1+y2)/2)
Slopem = (y2-y1)/(x2-x1)
Line Equationy = mx + b
Circle
AreaA = πr²
CircumferenceC = 2πr
Triangle
AreaA = ½bh
CentroidG = ((x1+x2+x3)/3, (y1+y2+y3)/3)
Pythagorean Theorema² + b² = c²
Conic Sections
Parabolay = a(x-h)² + k
Ellipse AreaA = πab
Hyperbola(x-h)²/a² - (y-k)²/b² = 1
Free Online Geometry Calculator
Free online geometry calculator — calculate area, perimeter, volume, angles, and coordinates for 2D and 3D shapes. Includes interactive construction tools, a 3D surface grapher, and a built-in formula reference. No download, runs in any browser.
A Single Workspace for 2D Constructions, 3D Surfaces, and Shape Calculations
This geometry tool combines three capabilities that are usually spread across separate apps: a 2D shape calculator (area, perimeter, angles for triangles, circles, rectangles, trapezoids, and polygons), a 3D solid calculator (volume and surface area for cylinders, spheres, cones, prisms, and pyramids), and a construction canvas where you draw points, lines, circles, and polygons with compass-and-straightedge precision. Every result displays the exact formula used and the substitution step with your values plugged in — so you see the geometry, not just the answer.
The 2D construction tools include point, line, circle, arc, ellipse, triangle, polygon, spline, and Bezier curve drawing. You can measure distances, angles, and areas directly on the canvas. The 3D mode plots surfaces as functions z = f(x,y), parametric surfaces, or scatter plots from lists — with rotation, zoom, pan, wireframe toggle, and a plane slicer to examine cross-sections. Students preparing for SAT, ACT, or geometry finals can use the built-in formula reference sheet covering all standard shape formulas.
A Quick Tour of the Geometry Workspace: Shapes, Constructions, and 3D Views
If you have never used an online geometry tool before, here is the fastest way to get started:
Pick your shape. For 2D area and perimeter, select from circles, triangles, rectangles, trapezoids, or regular polygons. For 3D volume, choose cylinders, spheres, cones, prisms, or pyramids.
Enter dimensions. Type the radius, side length, height, or base measurements. The input fields are labeled with the dimension name so you know exactly what to enter.
Read the result. The calculator displays area/perimeter (2D) or volume/surface area (3D), along with the formula used and the step-by-step substitution.
Try the construction canvas. Switch to 2D Plane mode to draw shapes freehand. Select a tool (point, line, circle, polygon), click on the canvas, and drag. Measurements appear in the properties panel.
Explore 3D surfaces. Switch to 3D Grapher mode and enter a function like sin(x) + cos(y). Drag to rotate, scroll to zoom, and use the plane slicer to see cross-sections.
The Full Feature Set: 2D Shapes, 3D Solids, Constructions, and Surface Plotting
3D solids — cylinders, spheres, cones, rectangular prisms, pyramids (volume, surface area, base area, slant height)
Formula display — every result shows exactly which formula was used, with values substituted in
Construction canvas — draw points, lines, circles, arcs, ellipses, triangles, polygons, splines, and Bezier curves with measurement tools
3D surface grapher — plot z = f(x,y), parametric surfaces, and 3D scatter plots with rotation, zoom, wireframe, and plane slicer
Built-in formula reference — quick-access cheat sheet for all standard geometry formulas
Keyboard shortcuts — S (select), P (point), L (line), R (rectangle), C (circle), T (triangle), G (polygon) and more
Runs in any browser — reliable on Chromebooks during exams and in classrooms with spotty WiFi
Calc84 geometry calculator — 3D surface plots and 2D geometric constructions in one workspace.
How Do I Calculate the Volume of a Cone? — Worked Example
Say you need the volume of a cone with radius 4 cm and height 9 cm. Select "Cone" from the 3D shapes, enter r = 4 and h = 9. The calculator applies V = (1/3)πr²h, substitutes the values: V = (1/3) × π × 4² × 9 = (1/3) × π × 16 × 9 = 48π ≈ 150.80 cm³. The formula display shows each substitution step so you can follow the arithmetic. Compare this to looking up the formula in a textbook and doing the calculation by hand — the result is identical, but the step-by-step display helps you internalize the formula for test day.
For students moving into calculus, understanding 3D geometry is essential groundwork. Visualizing how a curve rotates around an axis to create a surface of revolution — the idea behind solids of revolution in integral calculus — starts with knowing the volume of basic solids like cylinders and cones. The 3D grapher shows volume and surface area side by side, so the relationship between them becomes intuitive before you see an integral sign.
Which Shapes Does This Geometry Calculator Cover?
The geometry calculator covers the complete set of shapes found in high school and introductory college geometry. For 2D shapes: circles (area, circumference, arc length, sector area), triangles (right, equilateral, isosceles — area via base×height or Heron's formula, perimeter, Pythagorean theorem for right triangles), rectangles (area, perimeter, diagonal), trapezoids (area via average of bases × height), and regular polygons (area and perimeter for any number of sides). For 3D solids: cylinders (volume, lateral surface area, total surface area), spheres (volume, surface area), cones (volume, lateral surface area, total surface area, slant height), rectangular prisms (volume, surface area, diagonal), and regular pyramids (volume, surface area, base area, slant height).
Architecture and engineering students use this tool for area and volume checks during design coursework. SAT and ACT math sections include 3-5 geometry questions on average, covering area, perimeter, volume, and the Pythagorean theorem — all handled by this calculator. The construction canvas is also useful for demonstrating geometric proofs and transformations visually.
Common Questions About Working With 2D Shapes and 3D Solids
Is this geometry calculator free?
Yes, completely free. All shapes — 2D and 3D — work without signup, download, or payment. There is no limit on how many calculations you can run. The construction canvas and 3D grapher are also fully free with no feature restrictions.
Does it show the formula used for each calculation?
Yes. Every result includes the exact formula — for example, "A = (1/2)bh" for triangle area or "V = πr²h" for cylinder volume. The substitution step shows your values plugged into the formula, so you can follow the work and catch input mistakes before they become wrong answers.
Can it calculate 3D shapes like cylinders and spheres?
Yes. The 3D geometry section handles cylinders, spheres, cones, rectangular prisms, and regular pyramids. For each shape, you get volume, surface area, and (for prisms and pyramids) base area. Results use the same formulas found on the College Board Math Reference Sheet.
What is the difference between the 2D Plane and 3D Grapher modes?
The 2D Plane mode is a construction canvas — you draw shapes (points, lines, circles, polygons) with drawing tools and measure distances, angles, and areas. The 3D Grapher mode plots mathematical surfaces like z = sin(x) + cos(y) and lets you rotate, zoom, and slice through them. Use 2D for geometry homework and constructions; use 3D for visualizing multivariable functions and solids.
Does it include a Pythagorean theorem calculator?
Yes. For right triangles, enter any two sides and the calculator finds the third using a² + b² = c². The formula display shows which side is being solved for and the full working. This is the most commonly used feature by geometry students during homework.
Can I use this on a phone or tablet?
Yes. The geometry calculator is fully responsive. On touchscreens, the construction canvas supports tap-to-place points and pinch-to-zoom. The shape calculators stack vertically on narrow screens. All features — 2D, 3D, formula display, construction tools — work identically on mobile and desktop.
Students who pair this geometry workspace with the TI-84 graphing calculator online walkthrough get the same coordinate-style thinking applied to functions, and the AI equation solver comes in handy when a geometry problem turns into a system of equations to solve.
Page last updated: August 4, 2026
Miqdad Qaisrani
Full Stack Engineer & Creator of Calc84
Miqdad built Calc84's geometry tool to give students a free, interactive way to explore constructions and 3D surfaces. He's a full-stack engineer focused on visual math tools.
TI-84 Plus CE is a trademark of Texas Instruments Incorporated. Calc84 is an independent educational project by Miqdad Qaisrani, not affiliated with or endorsed by Texas Instruments. Full disclaimer.
