The Geometry Tool is a constraint-based geometry construction workspace: objects are defined in terms of other objects, and when a parent moves, every dependent updates live. The canvas, definition list, and measurements stay in sync.
Construct geometry online
The Geometry Tool opens on a coordinate plane with a toolbar for select, point, segment, line, ray, vector, circle, polygon, perpendicular, parallel, midpoint, angle bisector, intersection, compass, and measure. A numbered definition list on the side names each object with a human definition such as “C = midpoint of AB.” Snapping prefers existing points, midpoints, on-curve positions, and grid points so constructions stay exact.
Draw points, lines and circles
Point mode places labeled free points. Clicking on a line or circle while placing creates a constrained point that slides on that path. Segment, line, ray, and vector modes take two points. Circle mode uses a center and a radius point; the radius updates when either point moves. Polygon mode clicks vertices in order and closes on the first vertex.
Construct perpendicular, parallel, midpoint and more
Perpendicular and parallel tools pick a line (or segment) then a through-point and add a live constraint line — not baked free endpoints. Midpoint stays the midpoint under drag. Intersection points follow both parents. Angle bisector takes three points. Compass copies a circle’s radius to a new center.
Measure length, angle and area
The Measure tool attaches live labels: segment length, angle in degrees, polygon area, and circle area/circumference. A 3-4-5 right angle reads 90.0°, a unit square area reads 1.00, and a circle of radius 2 reads area and circumference near 12.57. Values refresh on every recompute; display decimals are adjustable.
Drag points to explore constructions
Select mode drags free points and constrained points along their paths. The solver recomputes only descendants of the moved node. Undo/redo covers construct, move (one step per drag), and delete. Deleting a parent warns when dependents will cascade. Pan with empty-canvas drag or Space-drag; scroll to zoom; double-click empty canvas to reset the view. Esc cancels an in-progress construction. Save and load JSON locally; export PNG or SVG. Autosave keeps the working construction across refresh.
Frequently asked questions
How do I construct a perpendicular line?
Choose Perpendicular, click a line or segment, then click the point the perpendicular should pass through. The perpendicular stays 90° as you drag the reference.
How do I measure an angle?
Choose Measure and click three points (vertex in the middle), or pick an existing angle structure. The stamp-colored label updates live.
Can I drag points?
Yes. Choose Select, then drag a free point. Constrained points (hollow) move only along their line or circle. Midpoints, intersections, and measures follow automatically.
How do I find the area of a polygon?
Choose Polygon, click vertices in order, and click the first vertex again to close. Then choose Measure and click the polygon, or read the live area in the measure bar.
Is the geometry tool free?
Yes. The Geometry Tool is free on Quick Calculators.
Summary
The Geometry Tool is the construction instrument in Math Tools: a constraint graph with a full construction palette, live measures, definition list, undo/redo, snap, pan/zoom, and save/load. It cross-links to Geometry Calculators for static formula pages and to the Graphing Calculator when a figure should become a plotted equation.