How to Measure Equipment for a Custom Flight Case: Dimensions, Weight, and Clearance Rules

I once ordered a custom case for a 2U amplifier, measuring it at 19 inches wide, 14 inches deep, and 3.5 inches tall. The case arrived, and the amplifier didn’t fit—I had forgotten to account for the rack ears, which added 1/4 inch to each side, and the power connector, which added 2 inches to the depth. The case was 1/2 inch too narrow and 2 inches too shallow. The manufacturer charged me a $50 restocking fee and 4 weeks of lead time to build a new case. That quarter-inch error cost me $50 and a month of delay. Getting accurate measurements is the most critical step in ordering custom flight cases. Even a quarter-inch error can result in a case that doesn’t fit, wasting time and money.

Basic Measurement Principles: Measure Twice, Order Once

Always measure equipment at its largest dimensions, including knobs, protrusions, and connectors. This sounds obvious, but it’s the #1 mistake people make—they measure the main body of the equipment and forget about the knobs, connectors, and feet that stick out. A guitar amplifier head might measure 19 inches wide at the body, but the knobs on the front panel stick out 1/2 inch, and the power connector on the back sticks out 1 inch. If you only measure the body, your case will be too small. Use a digital caliper ($15-30) for precision measurements and a tape measure ($10-20) for larger items. A digital caliper gives you measurements to 0.001 inch accuracy, which is essential for small parts and connectors. A tape measure is fine for large dimensions, but be aware that tape measures can sag on long measurements, causing errors of 1/8-1/4 inch.

Measure width, depth, and height independently. Don’t assume a piece of equipment is square or rectangular—measure each dimension separately. I once measured a mixer at 19 inches wide and assumed it was 19 inches deep, but it was actually 16 inches deep. That 3-inch error would have resulted in a case that was too deep, wasting space and adding unnecessary weight. Don’t forget to account for cable connectors that plug into the equipment—these often add 2-4 inches to the depth requirement. A power connector might add 1-2 inches, a speaker connector might add 2-3 inches, and a bundle of XLR cables might add 3-4 inches. Measure the equipment with all cables plugged in and connectors attached to get the true depth requirement. Measure twice, order once. I measure every dimension at least twice, and if the two measurements differ by more than 1/16 inch, I measure a third time. The 2 minutes it takes to measure twice is much cheaper than the $50 restocking fee and 4-week delay for a case that doesn’t fit.

Rackmount Equipment Measurement: The 1.75 Inch Rule

For 19-inch rackmount equipment, specify the rack unit (U) height. Standard rack units are 1.75 inches each. A 1U piece of equipment is 1.75 inches tall, a 2U is 3.5 inches, a 4U is 7 inches, and so on. Measure actual equipment height to confirm it fits the specified U size—some equipment is slightly taller than its rated U size. I’ve seen 2U amplifiers that are actually 2.1U tall (3.675 inches), which means they don’t fit in a standard 2U rack space. If you’re building a custom rack case, measure each piece of equipment individually and add up the actual heights, don’t just add up the U ratings. Specify rack depth based on deepest equipment plus cable management space. A standard rack case might be 18 inches deep, but if your deepest equipment is 16 inches deep and you need 4 inches for cable management, you need a 20-inch deep case.

Allow 3-4 inches behind equipment for cable routing and connectors. This is another common mistake—people measure the equipment depth and forget to leave space for cables. If you don’t leave enough space, you’ll either have to bend cables at sharp angles (which can damage them) or leave the rack door open (which defeats the purpose of a case). For mixed-depth racks, specify variable-depth rails. If you have a 16-inch deep amplifier and a 10-inch deep effects processor in the same rack, variable-depth rails let you mount each piece at the appropriate depth, rather than forcing everything to the same depth. Consider ventilation when measuring rack equipment—amplifiers and other heat-generating equipment need airflow. Add 1-2U of blank space above heat-generating equipment, and consider vented rack panels or fans if the equipment runs hot. A $20 fan or vented panel is cheaper than a $500 amplifier repair caused by overheating.

Irregular and Odd-Shaped Equipment: When a Tape Measure Isn’t Enough

For equipment that doesn’t fit standard dimensions, create a dimensional drawing with all critical measurements marked. This is essential for instruments, custom-built gear, and anything with an irregular shape. A dimensional drawing doesn’t need to be fancy—a simple sketch with measurements marked is sufficient. The key is to mark every critical dimension: width at the widest point, depth at the deepest point, height at the tallest point, and any protrusions or irregularities. Take photos from multiple angles. Photos help the case builder understand the shape of the equipment, especially if there are irregularities that are hard to describe in words. Take photos from the front, back, top, bottom, and both sides—6 photos total. This takes 2 minutes and can prevent measurement errors.

For instruments, measure body dimensions, neck length, and headstock width separately. A guitar might have a body that’s 16 inches wide, but the headstock might be 4 inches wide and stick out at an angle. If you only measure the body, your case won’t accommodate the headstock. Measure the neck length separately, because the neck is often the longest dimension of the instrument. Consider removable components like microphone stands, pedal boards, and power supplies that need dedicated compartments. These components often get forgotten in the initial measurement, but they need space in the case. If you forget to measure them, you’ll end up with a case that doesn’t have room for all your gear. When in doubt, provide a physical template or send the equipment to the case manufacturer for custom fitting. A physical template (made from cardboard or foam board) is the most accurate way to ensure a perfect fit, because the manufacturer can trace the exact shape. Sending the equipment to the manufacturer is even more accurate, but it means you’ll be without the equipment for a few days. If the equipment is valuable or hard to replace, consider making a template instead of sending the equipment.

Accessory and Cable Space Planning: The 10-15% Rule

Don’t forget to allocate space for accessories. Cables, power supplies, adapters, and spare parts all need dedicated compartments. This is another common mistake—people measure the main equipment and forget about all the accessories that go with it. A mixer case might need space for 10 XLR cables, 2 power cables, a power strip, and a spare bulb. If you don’t plan for these, you’ll end up carrying them in a separate bag, which defeats the purpose of a custom case. Specify cable lengths and connector types for proper foam cutout sizing. A 10-foot XLR cable coiled up is about 6 inches in diameter; a 25-foot XLR cable is about 10 inches in diameter. If you specify the cable lengths, the manufacturer can cut foam compartments that are the right size.

For touring rigs, plan for spare cables and emergency repair kits. A touring rig should always have spare cables, fuses, batteries, and basic tools. These need dedicated space in the case. Consider future expansion—leave 10-15% extra space for additional equipment or accessories you may add later. If you’re building a case for a current rig that you plan to expand in the next year, leave room for the expansion. It’s much cheaper to build a slightly larger case now than to build a new case later. I once built a case for a 4-piece band’s monitor system, and 6 months later they added a 5th monitor. The case didn’t have room for the 5th monitor, so they had to carry it in a separate bag. If I had left 10-15% extra space, the 5th monitor would have fit. Accurate measurements are the foundation of a perfect-fitting flight case. Spend 15-20 minutes measuring carefully, and you’ll avoid the $50 restocking fee and 4-week delay I experienced. The math isn’t complicated—measure twice, account for cables and connectors, leave room for accessories, and you’ll get a case that fits perfectly the first time.

Custom flight cases engineered and produced in Changzhou’s aluminum case manufacturing cluster. OEM/ODM partner with our partner factories operating under ISO 9001 quality systems.

Measurement Tools Comparison

Choosing the right measurement tool ensures accuracy. Here’s a comparison of common tools:

Common Measurement Mistakes & Solutions

1. Forgetting cables and connectors: Measure equipment with all cables plugged in and connectors attached. Add 2-3″ clearance for cable bend radius.
2. Ignoring heat dissipation: Amplifiers and rack gear need ventilation. Add 1-2U of blank space above heat-generating equipment.
3. Measuring only the widest point: Equipment often has protruding knobs, antennas, or feet. Measure at the widest, deepest, and tallest points.
4. Not accounting for foam thickness: Custom foam inserts typically add 1-2″ per side. Subtract foam thickness from interior dimensions when calculating fit.
5. Rounding down instead of up: Always round up to the nearest 1/4″. A slightly loose fit is better than a case that won’t close.

Measurement Checklist for Touring Professionals

• □ Width (left to right) at widest point
• □ Depth (front to back) including knobs and connectors
• □ Height (top to bottom) including feet and antennas
• □ Weight (empty and loaded)
• □ Center of gravity (for handle placement)
• □ Cable entry/exit points
• □ Ventilation requirements
• □ Special handling needs (fragile items, temperature-sensitive)
• □ Photos from all angles (front, back, top, sides)
• □ Brand/model numbers for reference

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