Choosing the right understring radius gauges can make setup work faster, more accurate, and far less frustrating. Whether you are dialing in a guitar, bass, or a small repair bench, the right gauge helps you match the fretboard radius without guesswork.
In this roundup, we focus on practical tools that suit both home players and working techs, with an eye on accuracy, durability, and value.
Best 9 Under String Radius Gauges Picks for 2026
Best Radius Range Coverage
Dreamtop 9-Piece Understring Gauges
- 9 common radii from 7.25" to 20"
- Checks fretboard, saddle, and nut radius
- Stainless steel, slim, and easy to use
Best For: Guitarists, bass players, and DIY luthiers who want a broad, affordable radius-gauge set.
Best for Fast Setup Checks
StewMac String Action Gauge & Ruler
- Progressive string-height scale speeds up action checks
- Measures nut height, saddle depth, and polepiece height
- Durable stainless steel build with shop-friendly accuracy
Best For: Techs and players who want one versatile setup tool for fast, accurate string-height measurements.
Best for String-Change Accuracy
StewMac Understring Radius Gauges
- Nine common radii from 7-1/4" to 20"
- Fits standard 6-string guitars and most 4-string basses
- Low-profile design works with strings in place
Best For: Players and techs who want a reliable string-on radius gauge set for accurate setups.
Best Multi-Tool Kit
15-Piece Guitar Luthier Setup Set
- Multiple under-string radius gauges for common fingerboard radii
- 32-blade feeler gauge covers precise setup measurements
- Handy action ruler for strings, saddles, and nut checks
Best For: Players and beginner luthiers who want an affordable all-in-one guitar and bass setup kit.
Best Value Multi-Radius Set
Piutouyar 9-Piece Understring Radius Gauge
- 9 radii from 7.25" to 20"
- Stainless steel, rust-resistant build
- Works above or below the strings
Best For: Players and luthiers who need a budget-friendly multi-radius gauge set for guitars and basses.
Best Radius Range Kit
Mudder 10-Piece Luthier Tool Set
- 9 understring radius gauges cover many common setup sizes
- Double-sided ruler handles action, nut, bridge, and pickup checks
- Stainless steel build is durable and rust-resistant
Best For: Players who want a compact, affordable all-in-one setup kit for guitars and basses.
Best Radius Range Set
9-Piece Guitar & Bass Radius Gauges
- 9 common radius sizes from 7.25" to 20"
- Durable stainless steel construction
- Useful for guitar and bass setup work
Best For: Players and luthiers who want one versatile gauge kit for frequent setup checks.
Most Complete Setup Kit
10-Piece Guitar Radius Gauge Set
- 9 under string radius gauges cover common radii
- Includes a separate string action height ruler
- Stainless steel build for durable bench use
Best For: Players and DIY luthiers who want a compact all-in-one setup kit for radius and action checks.
Best for Multi-Scale Setup
Understring Guitar Radius Gauge, 9-Piece Set
- 9 common radii from 7.25 to 20 inches
- Stainless steel for durable, repeatable use
- Good for guitars, basses, and acoustic-electric instruments
Best For: Setup-focused players and techs who want one compact gauge set for multiple instrument radii.
Best Radius Range Coverage – Dreamtop 9-Piece Understring Gauges
If you need under string radius gauges for fast fretboard and saddle checks, this 9-piece Dreamtop set covers the most common guitar and bass radii in one compact stainless steel kit. It’s a practical choice for setup work when you want quick, repeatable measurements from either above or below the strings.
Best For: Guitarists, bass players, and DIY luthiers who want a broad, affordable radius-gauge set for routine setup and adjustment.
Pros:
- Includes 9 popular radii from 7.25" to 20" for broad compatibility
- Works for checking fretboard, saddle, and nut radius during setup
- Stainless steel build keeps the gauges thin, durable, and easy to handle
- Useful for electric guitar, acoustic guitar, and bass maintenance
Cons:
- Not a full luthier toolkit, just the radius gauges themselves
- Markings and thin profiles may take a moment to read accurately
- Best suited to radius matching, not more advanced repair tasks
For players who regularly tweak action and bridge height, these under string radius gauges offer a simple, no-frills way to match your instrument’s radius without guesswork. The wide size range makes them especially handy if you set up different guitars or basses at home.
Best for Fast Setup Checks – StewMac String Action Gauge & Ruler
If you want one of the most practical under string radius gauges for guitar and bass work, this StewMac stainless steel ruler stands out for speed and repeatability. It combines action, saddle slot, nut height, and polepiece measurements in one compact tool, so you can move through a setup without constantly swapping gauges.
Best For: Techs, luthiers, and players who want a single, durable setup tool for quick string-height and component checks on acoustic or electric instruments.
Pros:
- Progressive string-height scale makes action readings fast and easy
- Measures multiple setup points, including nut height and saddle slot depth
- Stainless steel build is made to hold up over years of shop use
- Original StewMac design with helpful backside conversion chart
Cons:
- Not a dedicated radius-only gauge, so it’s broader than some specialty tools
- Best results still depend on careful technique and good lighting
For players comparing under string radius gauges, this is less about matching one specific radius and more about getting fast, reliable setup measurements from a trusted shop tool. It’s a strong pick if you value versatility, accuracy, and a ruler you can keep in the case or workbench for the long haul.
Best for String-Change Accuracy – StewMac Understring Radius Gauges
If you want under string radius gauges that make setup work faster and more consistent, this StewMac 9-piece set is built for routine guitar tech tasks. The low-profile design lets you check fingerboard and saddle curvature with the strings still on, which is especially handy during quick adjustments.
Best For: Guitar techs, luthiers, and players setting up 6-string guitars or most 4-string basses who want an accurate, string-on radius matching tool.
Pros:
- Includes nine common radii from 7-1/4" to 20" for broad setup coverage
- Standard width fits string spreads up to 2-5/8" for most guitars and basses
- Low-profile shape works well without removing strings
- Backed by StewMac’s Lifetime Promise and support
Cons:
- Priced more like a pro-shop tool than an entry-level accessory
- Not intended for wider string spacing instruments
For anyone who needs dependable under string radius gauges during regular setup work, this set covers the most common fingerboard radii and stays practical enough for repeated use. It’s a strong fit if you value precision, durability, and a string-on workflow.
Best Multi-Tool Kit – 15-Piece Guitar Luthier Setup Set
If you want one compact kit that covers most common setup checks, this 15-piece set is a practical way to handle under string radius gauges, action height, and basic relief measurements without piecing together separate tools. The stainless steel gauges are durable and the included rulers make it easy to check a guitar or bass at home or on the bench.
Best For: Players, hobbyists, and beginner luthiers who want an all-in-one setup kit for guitar and bass maintenance.
Pros:
- Includes under-string radius gauges in multiple common sizes for quick fingerboard matching
- 32-blade feeler gauge covers a wide range of spacing and relief checks
- String action ruler adds useful measurements for saddles, nut slots, and pickup height
- Stainless steel build helps resist rust and holds up well over time
Cons:
- Notched radius gauge selection is useful, but not as specialized as dedicated pro sets
- Best suited for setup work, not for advanced repair or fret-dressing tasks
This is a strong value pick if you need under string radius gauges plus the other basics in one package. It won’t replace high-end shop tools, but for routine setup work it gives you the measurements most players actually need.
Best Value Multi-Radius Set – Piutouyar 9-Piece Understring Radius Gauge
Piutouyar’s 9-piece set is a practical option if you want under string radius gauges that cover the most common fretboard curves without much bulk. The stainless steel build keeps the tools rigid and rust-resistant, while the compact format makes them easy to store in a bench kit or gig bag for quick setup work.
Best For: Players and luthiers who want an affordable, portable radius gauge set for checking string radius on guitars and basses.
Pros:
- Includes 9 common radii, from 7.25″ to 20″, for broader setup coverage
- Stainless steel construction feels durable and resists corrosion
- Useful for measuring radius from above or below the strings
- Lightweight, compact, and easy to carry
Cons:
- No extra case or handle, so it’s a simple tool-only package
- Manual measurements may vary slightly from piece to piece
For everyday setup tasks, this set offers a straightforward way to compare fretboard and string curvature with under string radius gauges that cover a wide range of instruments. It’s especially appealing if you want a low-cost, no-frills tool set that still feels sturdy enough for regular use.
Best Radius Range Kit – Mudder 10-Piece Luthier Tool Set
If you want a compact setup kit that covers multiple instrument profiles, this Mudder set is a practical pick. It combines under string radius gauges in several common sizes with a double-sided action ruler, making it easier to check neck radius and string height without piecing together separate tools.
Best For: Guitar and bass players who want an affordable, all-in-one measuring kit for basic setup work.
Pros:
- Includes 9 understring radius gauges for a wide range of common fretboard and saddle radii
- Double-sided action ruler measures string height, bridge height, nut slot depth, and pickup height
- Stainless steel construction is durable, rust-resistant, and easy to store in a toolbox or gig bag
Cons:
- Sharp edges may require gloves or extra care during handling
- Not the most specialized option for professional luthiers needing premium calibration tools
For players who regularly fine-tune their own setups, this kit covers the essentials in one place and keeps measurements straightforward. The range of under string radius gauges adds flexibility, while the ruler helps verify action-related details for more precise adjustments.
Best Radius Range Set – 9-Piece Guitar & Bass Radius Gauges
If you need under string radius gauges for full setup work, this 9-piece stainless steel set covers the most common guitar and bass radii from 7.25″ to 20″. It’s a practical choice for checking fretboard, saddle, and nut radius during repair, adjustment, or a new setup.
Best For: Guitarists, bass players, and luthiers who want a versatile radius gauge kit for routine setup and maintenance.
Pros:
- Includes 9 common radii, giving you broad coverage for many instruments
- Stainless steel construction feels durable and resists rust and wear
- Works from above or below the strings for flexible setup checks
- Compact, lightweight design is easy to store in a gig bag or tool case
Cons:
- No carrying case or organizer included
- May be more than casual players need for occasional use
This set is a straightforward, no-frills option if you want under string radius gauges that cover the most useful sizes in one kit. It’s especially appealing for players who do their own setups and need reliable radius checks without paying for specialty tools.
Most Complete Setup Kit – 10-Piece Guitar Radius Gauge Set
If you want a compact setup kit that covers both curvature matching and string height checks, this 10-piece set is a practical pick. The included under string radius gauges cover the most common fretboard sizes, while the action ruler adds another useful measurement tool for quick guitar or bass adjustments.
Best For: Players and hobby luthiers who want an all-in-one tool set for basic setup work, especially matching radius and checking action.
Pros:
- Includes 9 under string radius gauges plus a string action height ruler
- Stainless steel construction helps resist rust and wear
- Covers common radius sizes from 7.25″ to 20″
- Portable kit is easy to store in a bench drawer or gig bag
Cons:
- Not a specialized pro-grade precision set
- May be more tool than needed for occasional players
This kit is a strong value if you regularly do setup work and want multiple under string radius gauges in one affordable package. It keeps the essentials together, making it easier to check fretboard radius and action without buying separate tools.
Best for Multi-Scale Setup – Understring Guitar Radius Gauge, 9-Piece Set
If you want a simple way to match bridge saddle height to fingerboard curvature, this 9-piece set of under string radius gauges gives you the most common measurement points in one compact kit. The stainless-steel feel and clearly marked sizes make it a practical bench tool for quick guitar and bass setup work.
Best For: Players, techs, and hobby luthiers who need a versatile gauge set for routine setup and saddle adjustments on guitars or basses.
Pros:
- Includes 9 common radii from 7.25 to 20 inches.
- Stainless steel construction helps with durability and long-term accuracy.
- Works with electric guitars, acoustics, basses, and electric-acoustics.
- Compact, lightweight pieces are easy to store and carry.
Cons:
- Does not cover every possible fingerboard radius.
- More useful for setup work than for complete repair tasks.
For anyone who routinely dials in string action, these under string radius gauges cover the most common modern setups without adding much cost or clutter. It is a straightforward, workshop-friendly option when you want a broad radius range in a single kit.
How We Picked the Best Under String Radius Gauges
We looked for sets that cover the most common fretboard radii, offer clear markings, and are easy to use during string-up, relief checks, and bridge or saddle adjustments. We also favored tools with a slim enough profile to slide under the strings cleanly, plus materials that resist bending and wear.
For many buyers, understring radius gauges are part of a larger setup kit. That is why we considered whether a set stands alone as a basic radius tool or adds value by including an action ruler, feeler gauges, or other luthier essentials.
Quick Comparison: What Matters Most
The fastest way to narrow your choice is to think about your workflow. If you only need radius matching, a dedicated 9-piece gauge set is often the simplest buy. If you want one kit for multiple setup tasks, a combo pack with an action ruler may be better.
Also compare width and readability. Standard-width gauges tend to work well on most 6-string guitars and many basses, while wider or thicker tools can be less convenient under low strings. Clear laser-etched or stamped markings are worth prioritizing if you use the tools often.
Key Buying Factors for Under String Radius Gauges
Radius Coverage
Make sure the set includes the common radii you actually work on. Many guitar and bass setups revolve around a predictable range, so a broad 9-piece set is usually enough for most players and techs.
Thickness and Access
The best understring radius gauges should slide under the strings without forcing the setup. A thinner profile can make quick checks easier, especially on lower-action instruments.
Material and Durability
Stainless steel generally offers better longevity and a more professional feel than flimsy plated alternatives. It also helps the tool stay flat and accurate over time.
Markings and Usability
Look for legible markings, consistent radius cuts, and a layout that makes comparisons simple at a glance. If you work in dim lighting or move fast during setups, clarity matters more than extra accessories.
Who Should Buy Which Under String Radius Gauges?
Beginner players who want a straightforward setup aid should choose a basic dedicated gauge set. Guitar and bass owners who do their own maintenance may prefer a combo kit that includes action measurement tools. Working techs and repair shops are usually best served by a durable, clearly labeled set that can handle repeated use.
If you are buying Under String Radius Gauges for the first time, focus on fit, coverage, and readability before extras. The right tool should save time, improve consistency, and make setup work feel more controlled.