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How to Use a Height Gage
Guide · Updated October 28, 2026
A height gage measures vertical distances from a surface plate. Beyond scribing layout lines, it is the everyday inspection tool for step heights, hole centers and feature locations on the plate.
Compare to a known stack
Build an exact reference height with the free Gage Block Calculator, then zero the indicator on it.
Step by step
- Clean and soak: Wipe the plate, gage base and part, and let the part reach room temperature.
- Zero on the plate: Lower the probe or scriber to the plate and zero the digital readout, or note the vernier/dial reading.
- Use an indicator for accuracy: Mount a test indicator on the gage beam so you read by needle zero, not by feel; probe force then stays constant.
- Touch the feature: Bring the indicator onto the feature until the needle reads zero, and read the height.
- Measure steps: For a step height, zero on the lower face and read the upper face directly, or subtract the two readings.
- Compare to blocks: For tight tolerances, set a gage block stack equal to nominal, zero on it, and read the part as a plus or minus deviation.
- Lock and recheck: Recheck zero on the plate after a set of readings to catch drift.
Worked example
A part step is nominal 1.2500 in. Build 1.2500 from blocks (1.000 + 0.250), zero the indicator on the stack, then read the part step: +0.0003 in. The step is 1.2503 in.
Measuring hole centers
Indicate the bottom of the bore (lowest point) and the top (highest point); the center height is the average. Or put a pin gage in the hole and measure over the pin minus half its diameter.
Tips
- Check the gage itself with gage blocks.
- For scribing lines, see height gage layout.
- A worn plate shifts zero: surface plate care.
- Use pin gages for hole centers.
FAQ
How accurate is a height gage?
Typical digital height gages read to 0.0005 in (0.01 mm) with accuracy around ±0.001 in over 12 in; using an indicator against gage blocks improves comparison accuracy.
Should I use the scriber or an indicator to measure?
Use an indicator for measuring; the scriber is for layout. The indicator gives consistent contact force and reads by needle zero.
How do I measure a hole center height?
Read the bottom and top of the bore with an indicator and average them, or measure over a pin in the hole and subtract half the pin diameter.
How do I zero a height gage?
Lower the probe onto a clean surface plate and press zero, or zero on a gage block stack equal to the nominal height for comparison.
Why do my height gage readings change?
Dirt, temperature, a worn plate or varying contact force. Clean, soak, use an indicator and recheck zero.
Related guides and calculators
- How to check a height gage with gage blocks
- How to use a height gage for layout
- How to use a surface plate
- Surface plate care and checking
- How to build a gage block stack
- How to use a dial indicator
- Pin gage set basics
- How to use a surface gage
- How to Use a Depth Micrometer
- How to Use a Tool Presetter
- How to Check a Square with a Cylindrical Square
- All free machinist calculators
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General shop information only — follow your gage manufacturer's instructions and your quality system.