How to Read a Vernier Caliper: Simulator
How to Read a Vernier Caliper: Interactive Simulator
Slide the virtual caliper, guess the reading, then check your answer with the full working. Choose 0.1 mm, 0.05 mm or 0.02 mm resolution and practise with random questions.
Drag the sliding jaw (the vernier part) with a mouse or finger, use the position slider, or click the drawing and press the arrow keys (Shift + arrow = 1 mm). When zoomed in, swipe elsewhere on the drawing to scroll.
What is a vernier caliper?
A vernier caliper measures length with two scales: the main scale on the beam and the vernier scale on the sliding jaw. The vernier lets it read to 0.1 mm, 0.05 mm or 0.02 mm, far finer than a 1 mm ruler. The scale was introduced by Pierre Vernier in 1631; in Indonesia it is also called the nonius, after Pedro Nunes.
Parts of a vernier caliper
| Part | Use |
|---|---|
| Fixed and sliding lower jaws (outside jaws) | Grip the object to measure length, thickness and outside diameter |
| Upper jaws (inside jaws) | Measure inside diameters of holes, rings or tube mouths |
| Depth rod | Measures the depth of holes or slots |
| Main scale | Millimetre scale on the beam, usually numbered in cm |
| Vernier scale | Small scale on the sliding jaw for fractions of a millimetre |
| Locking screw | Locks the sliding jaw so the reading does not change |
| Thumb rest | Moves the jaw smoothly |
Resolution
| Resolution | Vernier divisions | Vernier length | Numbers on the vernier |
|---|---|---|---|
| 0.1 mm | 10 | 9 mm | each line = 0.1 mm |
| 0.05 mm | 20 | 39 mm (also 19 mm) | each number = 0.1 mm, lines in between = 0.05 mm |
| 0.02 mm | 50 | 49 mm | each number = 0.1 mm, each line = 0.02 mm |
How to read a vernier caliper
- Clean and close the jaws. The vernier 0 should line up with the main-scale 0; if not, note the zero error.
- Hold the object between the jaws, snug but not squeezed, square to the jaws.
- Tighten the locking screw.
- Read the main scale: the last millimetre line just left of the vernier 0.
- Read the vernier: find the one vernier line that lines up best with any main-scale line.
- Add the two.
Worked examples
Example 1: 0.1 mm caliper
The vernier 0 is just past 2.3 cm on the main scale and vernier line 7 lines up. What is the reading?
- Main scale = 2.3 cm = 23 mm
- Vernier = 7 × 0.1 mm = 0.7 mm
- Reading = 23 + 0.7 = 23.7 mm
Answer: 23.7 mm (2.37 cm), written (23.70 ± 0.05) mm.
Example 2: 0.05 mm caliper
The vernier 0 is between 41 and 42 mm. Vernier line 13, between the numbers 6 and 7, lines up. What is the reading?
- Main scale = 41 mm
- Vernier = 13 × 0.05 mm = 0.65 mm
- Reading = 41 + 0.65 = 41.65 mm
Answer: 41.65 mm.
Example 3: 0.02 mm caliper
The main scale reads 8 mm and vernier line 37 lines up.
- Vernier = 37 × 0.02 mm = 0.74 mm
- Reading = 8 + 0.74 = 8.74 mm
Answer: 8.74 mm.
Example 4: zero error
With the jaws closed, the vernier 0 sits right of the main-scale 0 and line 3 lines up (0.1 mm caliper). An object reads 15.6 mm. What is its true length?
- Zero error = +3 × 0.1 mm = +0.3 mm
- True length = 15.6 − 0.3 = 15.3 mm
Answer: 15.3 mm.
Common mistakes
- Reading the main scale from the edge of the sliding jaw instead of the vernier 0.
- Treating the vernier numbers as line numbers. On a 0.05 mm vernier, the number 3 means 0.30 mm (line 6), not 0.15 mm.
- Mixing up cm and mm.
- Reading at an angle (parallax).
- Squeezing or tilting the object.
- Forgetting to check zero error.
Vernier caliper or micrometer?
| Vernier caliper | Micrometer | |
|---|---|---|
| Resolution | 0.1 / 0.05 / 0.02 mm | 0.01 mm |
| Typical range | 0–150 mm | 0–25 mm per instrument |
| Measures | length, outside and inside diameter, depth | thickness and outside diameter |
| Example | test-tube diameter, hole depth | paper thickness, wire diameter |
Practise reading a micrometer screw gauge with its simulator too.
Frequently asked questions
What is the resolution of a vernier caliper?
Analogue calipers usually read to 0.1 mm, 0.05 mm or 0.02 mm, depending on the number of vernier divisions (10, 20 or 50). Digital calipers typically read to 0.01 mm.
What is a vernier caliper used for?
Measuring the length and thickness of small objects, outside diameters (lower jaws), inside diameters (upper jaws) and the depth of holes (depth rod).
What is the formula for a vernier caliper reading?
Reading = main scale + (number of the coinciding vernier line × resolution). Example: 23 mm + 14 × 0.05 mm = 23.70 mm.
Why is the result written with ±?
Every instrument has a resolution limit. Many school physics books write a single measurement as x ± ½ resolution, for example (23.70 ± 0.05) mm for a 0.1 mm caliper.
What is zero error?
Zero error occurs when the vernier 0 does not line up with the main-scale 0 with the jaws closed. Subtract it from every reading.
Vernier caliper or micrometer?
A micrometer is more precise (0.01 mm) but has a short range (usually 0–25 mm) and measures only thickness or outside diameter. A caliper has a longer range and also measures inside diameter and depth.
Equipping a laboratory?
AMI Scientific supplies chemicals and laboratory equipment to universities, research labs and industry, with formal quotations and tax invoices. Send us your equipment list and our team will prepare a quotation.
Other measuring and lab equipment: micrometer, analytical balance, graduated cylinder, volumetric flask, burette, thermometer, laboratory equipment and their uses.
