Microscopy & measurement · SL/HL
Scale Bar Actual Size Calculator
Measure the specimen and the scale bar on the same displayed/printed image.
Your values
Start with the example or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or input upload.
Result & working
ExampleThe calculator is loading. The worked example is also shown below.
Step-by-step working
The formula
actual specimen size = (image specimen length / image scale-bar length) × stated scale-bar length
| Symbol | Meaning |
|---|---|
| image lengths | Any matching ruler unit can be used because their ratio is dimensionless. |
When to use this calculator
This method remains valid when an image has been resized, provided the specimen and scale bar were resized together.
Worked example
The page opens with these example values. The result below is pre-generated for reference.
- image specimen / image scale bar = 42 / 12 = 3.5
- actual specimen size = 3.5 × 10 µm = 35 µm
35 µm
Common mistakes
- Measure the scale bar and specimen on the same copy of the image.