Turn any photo into a caliper for round things. Calibrate one known distance, then click the two ends of the diameter — Amplia returns the diameter, the circumference, and the enclosed area at once.
Any round object works — a pipe end, a tank lid, a tree trunk, a hole in a drawing. One known distance sets the scale; two clicks do the rest.
Drop in any image — phone photos (HEIC/HEIF) and TIFF convert automatically. No account needed, and there is a built-in sample image to try.
Mark two points (B1 and B2) on something whose size you know — a ruler laid in the shot, a coin, a standard brick — and enter that value with its unit. This one reference sets the scale for everything.
Pick the Circle tool and click two opposite points across the round object. The circle commits instantly — the label shows the diameter and area, and clicking it opens the circumference too.
Not quite on target? Drag either point and every value recomputes live. You can also recalibrate at any time — your circles are kept.
Every circle you draw is measured three ways, in the same notation you will see on the canvas and in exported reports.
The straight span between your two clicks — usually the number you came for: bore sizes, trunk thickness, wheel diameter.
Computed exactly as π × d. Handy when your real-world cross-check is a tape wrapped around the object.
The enclosed area, π × d² ⁄ 4 — for a tank footprint, a round tabletop, or a pipe’s cross-section.
On the canvas, a circle’s label shows the diameter and the area; click the label to open a details dialog with all three values. Need the radius? It’s half the diameter — no extra clicks.
The free Circle tool covers true circles photographed face-on; the PRO Ellipse tool picks up ovals and slightly tilted circles.
Click the two ends of the diameter and the circle commits instantly — no third click, no Finish button. You get the diameter, circumference, and area, with handles C1.1 and C1.2 you can drag to fine-tune. Free on every plan, no account needed.
Circle in the full feature tourThree clicks — the center, one end of the first axis, then the second axis — trace an oval object, or the oval a circle becomes when photographed slightly off square. It reports both axes, the circumference, and the area. A PRO tool.
Ellipse in the full feature tourPipes are sold by nominal size (DN / NPS), but a photo gives you the outside diameter. Measure the OD across the pipe end, then find the nearest match below.
| DN | NPS | OD (metric) | OD (imperial) |
|---|---|---|---|
| DN 15 | 1/2″ | 21.3 mm | 0.840 in |
| DN 20 | 3/4″ | 26.7 mm | 1.050 in |
| DN 25 | 1″ | 33.4 mm | 1.315 in |
| DN 32 | 1 1/4″ | 42.2 mm | 1.660 in |
| DN 40 | 1 1/2″ | 48.3 mm | 1.900 in |
| DN 50 | 2″ | 60.3 mm | 2.375 in |
| DN | NPS | OD (metric) | OD (imperial) |
|---|---|---|---|
| DN 65 | 2 1/2″ | 73.0 mm | 2.875 in |
| DN 80 | 3″ | 88.9 mm | 3.500 in |
| DN 100 | 4″ | 114.3 mm | 4.500 in |
| DN 125 | 5″ | 141.3 mm | 5.563 in |
| DN 150 | 6″ | 168.3 mm | 6.625 in |
| DN 200 | 8″ | 219.1 mm | 8.625 in |
Outside diameters follow the ASME B36.10 steel-pipe standard. Copper tube, PVC, and electrical conduit use different sizing systems — when in doubt, measure the OD on your photo and check the manufacturer’s chart against it.
A tilted circle can still be traced honestly as the oval it appears to be — that is the Ellipse tool, a PRO feature. The free fix is simpler and more accurate: reshoot with the camera square-on to the circular face.
Diameter and circumference come out in any distance unit; the enclosed area uses metric, imperial, or astronomical area units. Switch families any time — values convert instantly.
| Symbol | Name |
|---|---|
| nm | nanometer |
| μm | micrometer |
| mm | millimeter |
| cm | centimeter |
| m | meter |
| km | kilometer |
| Symbol | Name |
|---|---|
| in | inch |
| ft | foot |
| yd | yard |
| mi | mile |
| mil | mil (thou) |
| Symbol | Name |
|---|---|
| ftm | fathom |
| cb | cable |
| nmi | nautical mile |
| Symbol | Name |
|---|---|
| AU | astronomical unit |
| ly | light-year |
| pc | parsec |
| Symbol | Name |
|---|---|
| pt | point |
| pc | pica |
| Symbol | Name |
|---|---|
| mm² | square millimeter |
| cm² | square centimeter |
| m² | square meter |
| km² | square kilometer |
| ha | hectare |
| Symbol | Name |
|---|---|
| in² | square inch |
| ft² | square foot |
| yd² | square yard |
| mi² | square mile |
| ac | acre |
| Symbol | Name |
|---|---|
| AU² | square astronomical unit |
| ly² | square light-year |
| pc² | square parsec |
Anything round, photographed face-on.
Outside diameters of pipe ends, flanges, and fittings — calibrate on a ruler in the shot and read the OD without hunting for a caliper.
Trunk diameter from a face-on photo of a cut end, or the silhouette width of a standing tree — quick numbers for arborist and firewood estimates.
Wheel, rim, and tire diameters from a straight-on photo of the side of a vehicle, a bike, or the wheel itself.
Tank footprints, drum lids, and manhole covers — the diameter for the fit, the area for the footprint, from one straight-down shot.
Drill holes, bores, and cutouts on scanned technical drawings, calibrated on a dimensioned edge or the drawing’s scale bar.
Tabletops, mirrors, rugs, and planters from listing photos — check whether it fits before you drive out to pick it up.
Accuracy depends on the photo, not the tool. Measurements are reliable when the circular face is photographed square-on and the calibration reference sits on the same flat plane as the object. Photos taken at an angle, references at a different depth, and wide-angle lens edges all introduce error.
Yes. A photo carries no scale by itself, so the Circle tool stays disabled until you mark one known distance. The easiest trick: lay a ruler or tape measure flat next to the object before you shoot, then calibrate on it.
From the diameter you measured: circumference = π × diameter. The on-canvas label shows the diameter and area; click the label to open the details dialog with all three values — diameter, circumference, and area.
The app reports diameter, circumference, and area. The radius is simply half the measured diameter — no extra clicks needed.
A circle photographed at an angle projects as an oval. The honest fix is to reshoot with the camera square-on to the circular face. There is also an Ellipse tool (PRO) that traces oval shapes with three clicks and reports both axes, the circumference, and the area.
Yes — shoot the pipe from the side and measure straight across its silhouette with the Line tool: the silhouette width is the outside diameter. The Circle tool is for when the round face itself is visible.
Diameter and circumference come out in any distance unit across five families — metric, imperial, nautical, astronomical, and typography. The enclosed area uses metric (including hectares), imperial (including acres), or astronomical area units.
Not unless you save it. Used as a guest, the app measures entirely in your browser and the image never leaves your device. Saving a project (optional, free account) stores the image securely so you can reopen the project on other devices.
Open the tool and try it on the built-in sample image — no sign-up, no install. Two clicks across any round object, three numbers back.
Amplia