Find the center faster
Place a circular object or image over the Circle Ruler and align it with the bullseye. The Circle Ruler makes center finding easier because every ring shares the same origin.
Online Concentric Circle - center finder, bullseye, measure radius & diameter
The online circle ruler with concentric circles helps you find circle radius, diameter, and circumference. This circle ruler tool features a perfect center finder and bullseye function for locating the center point of circular objects. The digital circle gauge and virtual template in this circle ruler enable quick real-size calculations for circular objects. From jewelry design to engineering drawings, this circle ruler is your go-to tool for all circular tasks. The circle ruler supports multiple circle layers, making this circle ruler ideal for complex designs.
More Ruler Types
Ruler.im0
Screen Ruler
Screen Ruler
Quadrant
center origin
Concentric Circle
Measure Radius/Diameter
Protractor
Measure Angle
Circle Ruler Workflow
Use the Circle Ruler for radius, diameter, and center checks
The Circle Ruler adds concentric circles to a calibrated screen, so round objects, rings, caps, buttons, pipes, and design details can be compared against visible radius and diameter guides.
Read radius and diameter
Use the Circle Ruler to compare an edge against circle layers and then read radius, diameter, or circumference references. The Circle Ruler is especially useful for circular part checks.
Measure uploaded images
Upload a ring, lens, wheel, gasket, or layout image, then use the Circle Ruler to mark circular dimensions directly. The Circle Ruler helps make remote size discussions more concrete.
Fullscreen circular templates
Fullscreen mode gives the Circle Ruler more room for larger circles. A fullscreen Circle Ruler works well as a virtual template when printed templates or physical gauges are not nearby.
Concentric Circle FAQs
The Circle Ruler is designed for round objects and circular layouts. Use it for rings, caps, lenses, wheels, buttons, pipe openings, craft templates, and any object where center, radius, diameter, or circumference needs a visual reference.
Place the object or uploaded image over the concentric rings and move it until the edge matches the same ring all around. The Circle Ruler makes center finding easier because every visible circle shares one fixed origin.
Yes. After calibration, the Circle Ruler can compare the object edge against real-size circle guides. Use the radius from center to edge, or double the radius to estimate diameter. For precision work, confirm critical dimensions with a physical gauge.
Yes. Upload a ring, lens, gasket, wheel, dial, or circular drawing, then use the Circle Ruler to mark circular dimensions. This is useful when sharing a size question with a seller, engineer, jeweler, or designer.
Recalibrate the Circle Ruler after changing screens, browser zoom, or device orientation. Circular measurement still depends on real display scale, so calibration keeps the circle layers meaningful in centimeters or inches.
Fullscreen mode gives the Circle Ruler larger rings and less browser clutter. It is especially helpful for larger circular objects, center-finding work, and uploaded images that need more room for readable radius and diameter marks.