How to Choose a Capo: Fretboard Radius Explained
Why some capos buzz or pull strings sharp, what fretboard radius means, and how to match a capo pad to your guitar in a few minutes.
Short answer: Fretboard radius is how curved your fretboard is across its width. A capo pad that is flatter or more curved than your fretboard presses some strings too hard and others too lightly, which causes buzzing or strings going sharp. Pick a capo whose pad matches your radius, or one with interchangeable pads such as Thalia.
Most capo problems are blamed on the capo's spring or clamp. More often the cause is a mismatch between the shape of the pad and the shape of the fretboard.
What is fretboard radius?
Look down the neck from the headstock. Most fretboards are slightly curved, like a section of a large circle. The radius is the size of that circle in inches.
- Smaller number, more curve. A 7.25" board is noticeably rounded.
- Larger number, flatter board. A 16" board is close to flat. Classical guitars are often completely flat.
Typical values, which vary by model and year:
|
Guitar type |
Typical radius |
|---|---|
|
Vintage-style Fender |
7.25" |
|
Modern Fender and many Strat- or Tele-style guitars |
9.5" |
|
Gibson and many electric guitars |
12" |
|
Many steel-string acoustics |
12"–16" |
|
Classical guitars |
Usually flat |
Check your guitar's spec sheet on the maker's website to be sure.
Why does radius matter for a capo?
A capo has to press all six strings evenly.
- Pad too flat for the board: the outer strings, especially the low E, are pressed less firmly and can buzz.
- Pad too curved for the board: the middle strings, the D and G, get less pressure and can buzz.
- Too much clamping force to compensate: strings bend sharp and you have to retune every time you move the capo.
How do Thalia capos handle radius?
Thalia capos, which you will find in our strings and accessories collection, use interchangeable fretpads. A 12" pad comes pre-installed, and Thalia offers pads for 9.5", 10", 15", 16" and other profiles, plus XL pads for extra string pressure. Thalia's own troubleshooting rule is simple:
- Low E buzzes? Your radius is probably under 12". Try the 10" pad, then the 9.5".
- D or G strings buzz? Your radius is probably over 12". Try the 15" pad, then the 16".
- Still buzzing at the 1st or 2nd fret with every pad? Try the XL pads, which add pressure. Thin necks, compound-radius boards and 12-string guitars often need them.
Capo placement tips that prevent buzz and tuning drift
- Place the capo just behind the fret, not in the middle between frets.
- Clamp only as tight as needed for clean notes. Over-clamping pulls strings sharp.
- Retune quickly after placing the capo if your ear tells you to; small drift is normal on light-gauge strings.
- Remove the capo when you stop playing so the pad and the neck are not under constant pressure.
FAQ
Why does my capo make the guitar go out of tune? Usually too much clamping force, or a capo placed too far from the fret. Both bend the strings sharp.
Can one capo fit both acoustic and electric guitars? Yes, if the pad matches each fretboard's radius. Interchangeable pads make this easier.
How do I find my fretboard radius? Check the manufacturer's specs for your model. A set of radius gauges gives an exact reading, and trial with pads works too.
Do Thalia capos come with a warranty? Thalia states a lifetime mechanical warranty on its capos.