Measure at the 12th fret with a ruler or feeler gauge; record string height in mm or inches.

I’ve measured guitar action for decades as a player and tech, and this guide shows you exactly how to measure guitar action step by step. You’ll learn the tools, the setup, clear measuring methods for the nut, relief, and 12th-fret action, how to interpret results, and what to do next. Read on to master how to measure guitar action with confidence and get repeatable, usable data for setup or repair.

Tools you need to measure guitar action

To measure guitar action accurately you need a few basic tools. These tools help you get consistent measurements and avoid guesswork when adjusting action.

• String action ruler or action gauge that reads in mm and inches.
• Feeler gauges for nut slot checks and very small clearances.
• Capo to lock the nut or first fret when measuring relief.
• Digital tuner to keep the guitar in tune while measuring.
• Soft cloth and capo cushion to protect the fretboard during checks.

I always keep a simple action ruler and a set of feeler gauges in my kit. They are the fastest way to get repeatable measurements when I measure guitar action.

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Quick prep: setup before you measure

A few setup steps make your measurements accurate and useful. Skip them and your numbers can be misleading.

• Tune the guitar to pitch. Measure only when strings are stable.
• Clean strings and fretboard; grime can change clearances slightly.
• Wear or replace new strings if you plan to set action after measuring.
• Place the guitar on a stable surface or use a work cradle to avoid movement.

From my experience, measuring right after changing strings gives the most consistent baseline when you measure guitar action.

Step-by-step: how to measure guitar action

Follow these steps to measure guitar action at the nut, for neck relief, and at the 12th fret. I include both metric and imperial suggestions.

1. Prepare and tune

• Tune the guitar fully and let it settle for a few minutes.
• If measuring multiple times, retune before each measurement.

2. Measure nut slot height

• Press the string at the second fret with one hand.
• Use a feeler gauge or a business card to check the gap at the first fret between the bottom of the string and the top of the first fret.
• Record nut clearance (typical ranges: high E 0.10–0.30 mm, low E 0.20–0.40 mm). These vary by style.

3. Measure neck relief (truss rod check)

• Capo at the first fret or hold down the string at the first fret.
• Press the same string at the highest fret (usually where neck meets body).
• Measure the gap at the 7th or 8th fret between string and fret using feeler gauges or feel with a feeler gauge thickness chart; typical relief: 0.05–0.30 mm depending on play style.
• This tells you how much forward bow the neck has.

4. Measure action at the 12th fret (standard)

• Play or press the string at the first fret and at the last fret to flatten the string along the neck for a true relief reading, or simply let it settle tuned for action measure.
• Place the action ruler so it sits across the 12th fret and measure from the top of the 12th fret to the bottom of the string.
• Record heights for each string. Use mm and inches for clarity. Typical targets: electric guitars 1.2–2.5 mm (high E near 1.5 mm, low E near 2.0 mm); acoustic guitars 2.0–4.0 mm (high E near 2.5 mm, low E near 3.0 mm).

5. Repeat and average

• Measure all strings and take averages if you’re setting action.
• Note differences between strings — they often require saddle adjustments for balance.

I always measure at least twice and log numbers. When I measure guitar action, consistency matters more than one-off readings.

Standard action heights and what they mean

Knowing industry ranges helps you interpret measurements when you measure guitar action.

• Electric guitar typical target at 12th fret

  • High E string: about 1.2–1.8 mm
  • Low E string: about 1.8–2.4 mm

• Acoustic guitar typical target at 12th fret

  • High E string: about 2.0–3.0 mm
  • Low E string: about 2.8–4.0 mm

• Nut slot clearance

  • Electric: roughly 0.10–0.30 mm on treble strings
  • Acoustic: slightly higher for thicker strings

These ranges help you decide if action is low, medium, or high when you measure guitar action. Player preference, string gauge, and playing style change your ideal numbers.

Adjusting action after measuring

Once you measure guitar action you may need to adjust the nut, truss rod, or bridge. Here are safe steps and priorities.

• Fix relief first

  • If relief is excessive or absent, adjust the truss rod a quarter-turn at a time and let settle several hours before remeasuring.

• Adjust saddle or bridge next

  • Raise or lower the saddle to change 12th-fret action. On electric bridges, adjust individual saddle screws if necessary.

• Tweak nut slots last

  • If nut action is too high, file slots carefully or have a tech do it. If too low, replace the nut or add a shim.

Always make small changes and remeasure. My rule: change one thing at a time, then measure. That keeps results predictable when I measure guitar action and tune setups.

Common problems, troubleshooting, and tips

When you measure guitar action you may find issues that need more than basic tweaks. Here’s how I handle common cases.

• Buzz after lowering action

  • Check for high frets or insufficient neck relief. Lowering action can cause buzz if frets are uneven.

• String rattles at the nut

  • Nut slots may be too low. Use a shim or replace the nut to fix buzzing.

• Action varies across strings

  • Check saddle angle and individual saddle heights. Intonation adjustments sometimes affect perceived action.

• Environmental variation

  • Humidity and temperature change neck relief and action. Measure in consistent conditions for reliable results.

From experience, the most common mistake is rushing adjustments. I always measure guitar action before and after every small tweak, and I recommend you do the same.

Maintenance and when to re-measure

Measure guitar action regularly to keep playability consistent. Here’s a simple schedule I use.

• After a string change: measure and tune, then remeasure after 24 hours.
• Seasonal checks: measure every seasonal change if you live in a variable climate.
• After any repair or setup: always measure to confirm changes.

Keeping a small log of when and what you measured helps. I keep notes on string gauge, action at 12th fret, and truss rod turns whenever I measure guitar action for a client.

Frequently Asked Questions of how to measure guitar action

How do I measure guitar action with a ruler?

Tune the guitar, place a string action ruler across the 12th fret, and measure from the top of the fret to the bottom of the string. Record each string’s height in mm or inches for comparison.

Should I measure action at the 12th fret or 14th fret?

The 12th fret is the standard reference point for most guitars and gives a consistent baseline for comparing instruments. Some players measure at the 14th fret on certain electric guitars, but 12th is most common.

How do I measure nut action correctly?

Press the string at the second fret and use a feeler gauge to measure the gap at the first fret between the string and the top of the fret. Keep values small and consistent with your playing style.

What instruments do I need to measure neck relief?

You need a tuner, capo or method to hold the first fret, and a feeler gauge or ruler to measure the gap at the 7th or 8th fret. Measuring relief is best done after tuning and letting the strings settle.

How often should I measure guitar action?

Measure guitar action after string changes, seasonal humidity shifts, or any setup work. A simple schedule is after string changes and every few months in changing climates.

Conclusion

Measuring guitar action is a simple skill that gives you control over playability. Tune your guitar, use consistent tools, and measure nut clearance, neck relief, and 12th-fret height to form a clear baseline. Make one change at a time and remeasure to learn how each adjustment affects feel and tone. Take action now: measure your guitar today, log your numbers, and use them to make small, effective improvements. If this guide helped, leave a comment, subscribe for more setup tips, or try a basic setup and share your results.