How to measure with a USB microscope online
Updated
You don't need the program that came on the mini CD to measure with a USB microscope. Browsers can use any USB camera, so the whole job, from live view to a table of results, can happen in a browser tab. Here is how to do it with MeasureLab.
What you need
- A USB or digital microscope that works as a webcam (UVC). Nearly all of them do: if your computer's camera app can show the picture, it will work.
- A computer with Chrome or Edge on Windows, macOS, ChromeOS or Linux.
- Something of known length for calibration, such as a stage micrometer or a ruler.
1. Connect the microscope and start the live view
Plug the microscope in and open MeasureLab. If you have more than one camera, for example a laptop webcam, pick the microscope from the list, then click Start Microscope Camera. The browser asks once for permission to use the camera; allow it.
2. Focus and freeze a frame
Measurements are taken on a still frame, so nothing moves while you work. Focus, then click Freeze or press F. Each frozen frame is kept in the image strip, so you can capture several and come back to them.
3. Calibrate
Freeze a frame of your reference, choose Calibrate (K), draw a line along a known length and enter it, for example 1 mm. Calibrate again whenever you change the zoom. The calibration guide covers the details and the common mistakes.
4. Measure
Pick a tool from the toolbar and draw on the frozen frame:
| Tool | Shortcut | Measures |
|---|---|---|
| Line | L | Distance between two points |
| Rectangle | R | Width and height |
| Circle | C | Size of round features such as holes, cells or particles |
| Angle (Pro) | A | Angle between two lines |
| Area (Pro) | P | Area of an irregular shape traced as a polygon |
Each shape is labelled with its value in your calibrated unit. Use the Select tool (V) to move a shape, and add notes to the image with the Text tool (T).
5. Collect the results in a table
Every measurement lands in the measurement table next to the image. Name the columns after what you measure, for example "Length" and "Width", and work through your samples row by row. With a free account you also get the count, mean and standard deviation of each column; Pro adds a histogram and a box plot.
6. Export
Click Export CSV to download the table for Excel, Google Sheets or your statistics software, and save the frozen frame as an image with the measurements drawn on, for reports and documentation.
Tips for better measurements
- Light the subject evenly; a sharp, well-lit edge is easier to place a line on.
- Measure near the centre of the picture, where lens distortion is smallest.
- Keep the subject flat and at the same height as the calibration reference.
- Measure the same feature a few times and use the mean rather than one reading.
No microscope? Try a sample
You can upload any photo instead of using the live view, or open the sample image: a circuit board that is already calibrated, so you can start measuring straight away.