How To Measure A Viola: Professional Sizing And Instrument Fit Guide

To accurately measure a viola, measure the instrument's back length (LOB) along the center seam from the edge beside the neck button down to the bottom edge, excluding the button itself. To size a viola for a player, measure the distance from the middle of the neck to the center of the left palm with the arm fully extended parallel to the floor. These two metrics ensure both accurate instrument classification and optimal physical ergonomics to prevent playing injury.

Pre-Measurement Preparation & Equipment Checklist

Measuring a viola involves two distinct procedures: determining the physical dimensions of the instrument itself for classification or lutherie evaluation, and measuring the musician to ensure an ergonomically safe playing fit. Unlike violins, which adhere to standardized fractional sizing (such as 4/4, 3/4, or 1/2), violas are measured and classified primarily by their body length—specifically the Length of Back (LOB)—expressed in inches or millimeters.

Improper instrument sizing places severe stress on a player's left shoulder, wrist, neck, and spine. Sizing an instrument too large leads to chronic conditions such as tendinitis or muscular strain, whereas sizing an instrument too small restricts technical facility and dampens tonal projection.

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Essential Tools & Equipment

• Flexible Tailor’s Tape Measure: Used for measuring player arm length and instrument contours.
• Luthier Caliper or Rigid Precision Ruler: Used for flat projection measuring of the instrument body length without surface arching bias.
• Sizing Chart & Marker: For recording LOB, rib height, bout widths, and player arm span metrics.
• Clear, Flat Surface: A padded workbench or table with a micro-fiber towel to secure the viola during physical measurement.

Prerequisites & Standards

• Knowledge Standard: Understanding the distinction between Instrument Overall Length vs. Length of Back (LOB).
• Player Stance: The musician must stand upright, relaxed, and fully unencumbered by heavy outer clothing or bulky shoulder pads.
• Time & Cost Benchmarks: Process requires 5–10 minutes; equipment cost ranges from $5 to $25 for standard measuring tools.

Step-by-Step Viola Sizing and Measurement Workflow

Step 1: Measure Instrument Body Length (Length of Back / LOB)

Place the viola face-down on a soft, clean surface to protect the varnish, bridge, and soundpost. Locate the upper edge of the back where the wooden body meets the root of the neck.

1. Position the zero mark of your rigid ruler or flexible tape at the top edge of the back plate immediately adjacent to the neck button (the small semi-circular piece of wood extending from the back plate over the neck joint).
2. Extend the measuring tool straight down the center seam of the instrument back plate to the bottom edge adjacent to the endpin block.
3. Record the measurement strictly from edge to edge along the body plate.

Warning: Do not include the neck button or the endpin in your measurement. Including the button will artificially inflate the body length reading by 1/4 to 1/2 inch, leading to incorrect instrument classification.

Pro-Tip: Luthiers typically use a rigid straight caliper to measure the body's flat projection length, whereas instrument dealers often use a flexible tape over the arching. Be aware that measuring over high body arching with a soft tape can add 1/8 to 1/4 inch (3–6 mm) compared to a flat projection caliper measurement.

Step 2: Measure Player Arm Span for Sizing

To determine the correct viola size for a student or performing artist, calculate the player's physical reach.

1. Have the player stand completely upright with their back flat against a wall or standing freely with neutral posture.
2. Instruct the player to raise their left arm straight out to the side, perpendicular to the torso (at a 90-degree angle), parallel to the floor. The palm should face upward toward the ceiling, with fingers relaxed and straight.
3. Place the end of a flexible tape measure at the left side of the player's neck, right at the intersection where the neck joins the shoulder (near the collarbone).
4. Pull the tape flat along the underside of the extended left arm to the center of the open palm.
5. Note this measurement in inches or centimeters. This represents the Maximum Reach Measurement.
6. Next, slide the tape reading back to the wrist bone (where the palm meets the wrist joint). This represents the Minimum Comfortable Fit Measurement.

Step 3: Assess Physical Fit with the Instrument

Once you have paired the arm measurement to a theoretical viola size using standard dimensional charts, confirm the match dynamically with an actual instrument.

1. Place the selected viola on the player's left shoulder in standard playing position, bringing the chin comfortably rest upon the chinrest without twisting the neck.
2. Instruct the player to reach around the scroll with their left hand and wrap their fingers completely around the top of the scroll into the pegbox area.
3. Check the angle formed at the elbow joint. If the left arm is fully extended with zero bend at the elbow, or if the player cannot reach around the scroll to touch the pegbox, the viola is too large.
4. If the elbow forms a comfortable 100 to 120-degree angle and the fingers easily cup the scroll while the instrument sits on the shoulder, the sizing is ergonomically correct.

Pro-Tip: If a player lands directly between two standard viola sizes, select the smaller instrument. A slightly smaller instrument allows for optimal technical development and shift accuracy without causing physical strain.

Step 4: Measure Bout Widths and Scale Length (Advanced Luthier Metrics)

For full-size violas (15 inches and above), measuring only body length is often insufficient to judge ergonomics, as bout widths and neck scales vary widely among makers (e.g., Stradivari vs. Tertis or Maggini models).

1. Upper Bout Width: Measure across the widest point of the top body section using a sliding caliper.
2. Lower Bout Width: Measure across the widest point of the bottom body section.
3. C-Bout (Middle) Width: Measure across the narrowest point of the center body cutout.
4. Neck Scale & Stop Length: Measure from the edge of the top nut to the edge of the top plate at the neck joint (Neck Scale, standard ~150 mm on a 16" instrument), and from the edge of the top plate to the inner nicks of the f-holes (Stop Length, standard ~225 mm on a 16" instrument).

Viola Dimensional Standards & Player Arm Length Reference Matrix

Because violas lack fixed fractional standardizations like violins, the relationship between body length, instrument size, and player reach is mapped using specific physical ranges. Use this benchmark table to pair player arm length with instrument dimensions.

Erroneous Measurement Scenarios & Physical Diagnostic Fixes

Scenario 1: Sizing an Instrument by Overall Length Instead of Length of Back

• Root Cause: The user measures from the top of the scroll down to the bottom endpin button, confusing total physical length with acoustic body size. Scroll lengths vary significantly across makers, causing an incorrect body classification.
• Actionable Fix: Isolate the measuring tape strictly to the back wood plate (LOB). Disregard the scroll, pegbox, neck overhang, and endpin entirely when classifying viola size.

Scenario 2: Over-Sizing a Student to Allow "Room to Grow"

• Root Cause: Parents or teachers purchase a larger viola (e.g., a 15.5" or 16" instrument) for a developing student whose arm span only supports a 14" or 15" viola, aiming to save money on future upgrades.
• Actionable Fix: Measure the player's arm span using the neck-to-wrist (minimum fit) benchmark rather than maximum reach. If the left arm cannot bend at least 90 to 100 degrees while playing in first position, immediately drop down one body size to prevent severe muscular hyper-extension and shoulder injury.

Scenario 3: Disregarding Deep Rib Depths and Wide Bouts in Full-Size Violas

• Root Cause: A player with an arm span matching a 16.5" viola struggles with left-hand fatigue and collarbone pain, despite the LOB being technically correct.
• Actionable Fix: Measure the lower bout width and rib height of the instrument. Deep ribs (> 39 mm) or extra-wide lower bouts force the upper arm outward, increasing physical strain. Switch the player to a "small-pattern" 16.5" viola or a 16" wide-bout instrument with a narrow upper bout to reduce ergonomic reach.

Scenario 4: Measuring Player Arm Length with a Bent Elbow or Drooped Shoulder

• Root Cause: The musician relaxes their arm or drops their left shoulder during measurement, yielding an artificially short arm-span measurement.
• Actionable Fix: Ensure the player stands against a flat wall with posture fully extended, shoulder blades rested against the surface, and the left arm locked horizontally at a 90-degree angle parallel to the floor during tape placement.

Frequently Asked Questions

How is a full-size viola measured compared to a violin?

A violin is measured using standardized fractional sizes (where 4/4 is full size, measuring approximately 14 inches in body length). Violas do not use fractions; they are measured directly by the body length (Length of Back) in inches or millimeters, where a standard adult "full-size" viola ranges from 15.5 to 16.5 inches.

What is the most common full-size viola size for adult players?

The most widely played adult viola size is 16 inches (406 mm LOB). This size offers an optimal balance between rich lower-register resonance (C-string depth) and manageable physical ergonomics for the average adult arm span.

Can you measure a viola with a standard flexible sewing tape measure?

Yes, a flexible tailor's tape measure is ideal for determining player arm length and can be used to measure the body over the arching. However, for precise lutherie work or structural valuation, a rigid sliding caliper should be used to measure flat projection length down the center seam.

Why are 14-inch violas often confused with full-size violins?

A 14-inch viola shares the exact same back body length as a standard 4/4 full-size violin (355 mm). However, a 14-inch viola features wider bouts, deeper ribs, a thicker neck profile, and is strung with C-G-D-A pitch tuning using heavy-gauge viola strings.

What happens if a player uses a viola that is too large?

Using an oversized viola forces the musician to overextend the left shoulder, strain the forearm tendons, and twist the neck/spine to balance the instrument. Over time, this leads to chronic playing injuries, poor intonation in high positions, and slow finger facility.

Optimize Your Instrument Fit and Ergonomics

Selecting and measuring a viola correctly is the fundamental first step to achieving effortless technique and superior tone quality. If you are uncertain about choosing between two instrument sizes or require a professional measurement verification, consult with an accredited lutherie shop or experienced string pedagogue. Ensure your posture, technical performance, and long-term health remain protected by verifying your arm span against precise instrument dimensions today.