Carry‑on Luggage Size (mm to inches)

Capacity shown is an approximation. Shape factor reflects curves, lining, and compression; treat as guidance.

Airlines may measure including wheels and handles; some require smaller regional limits. Check the carrier’s published policy before travel.

Linear inches and regional examples

Linear inches sum up length, width, and height. Policies vary by region and route: North America often references 22 × 14 × 9 in or ≤ 45 linear inches; Europe often references ≤ 55 × 40 × 20 cm or ≤ 115 cm linear; Asia-Pacific often references ≤ 56 × 36 × 23 cm. Treat all figures as examples and verify your airline.

• Definition: linear inches = L + W + H
• Box vs linear: some carriers publish a three-side box, others a linear cap
• Drivers of variability: aircraft type, route, fare class, gate vs counter enforcement

Compute your linear total in mm and inches; save a screenshot of policy for quick reference.

Underseat personal item guide

Underseat items are designed to slide beneath the seat: laptop bags, compact backpacks, and tote bags. Common ranges are ≈ 40 × 30 × 15 cm to ≈ 45 × 35 × 20 cm (≈ 15.7 × 11.8 × 5.9 in to ≈ 17.7 × 13.8 × 7.9 in). Soft-sided bags compress; hard-shell cases rarely fit under the seat reliably.

• Depth matters most; shallow profiles fit better
• Rigid laptop sleeves reduce compressibility
• Ranges are illustrative; check your carrier’s specific underseat policy

Test at home with essentials loaded; remove bulky accessories if your bag barely fits.

Approximate capacity in liters

Estimate liters using the rectangular box formula (L × W × H) and adjust with a shape factor to reflect real-world curves, lining, and compression panels. Hard-shell ≈ 0.75–0.85; soft-sided ≈ 0.85–0.95.

• Box estimate (cm): liters ≈ (L × W × H) ÷ 1000
• Box estimate (in): liters ≈ (L × W × H) × 0.016387
• Expansion zippers increase size and liters but may break carry-on compliance

Round liters to whole numbers or one decimal place for clarity; treat as guidance.

What “20/22/24/26/28‑inch” really means

Retail labels seldom describe all three sides. The number may relate to a nominal height or a diagonal without wheels. Use the ranges as orientation and verify whether wheels and handles are included on the product page.

• “XX‑inch” often references nominal height/diagonal, not L × W × H
• Specs may omit wheels; add ≈ 2–4 cm to height for many designs
• Regions differ in naming conventions; always cross-check retailer specs

Keep personal notes for your bag in mm and inches to speed check-ins.

How to measure your luggage

Measure to the outermost protrusions, record in millimeters, convert to inches, and compute your linear total. Accurate measurement prevents surprises at the gate.

1. Prepare your bag on a flat surface
2. Measure length at the longest side, including wheels/corner guards
3. Measure width including any side handles
4. Measure height/depth at the thickest point
5. Record values in mm; convert to inches if needed
6. Add L + W + H; compare against your airline’s policy

Real‑world scenarios & policy FAQ

Example conversions

For custom sizes, use the main converter to input each side. Rounding shown to two decimals for readability.