Linear inches = Length + Width + Height. Airlines use this single number to set size limits for carry-on and checked baggage. The standard carry-on limit is 45 linear inches (approximately 22 × 14 × 9 in); the standard checked baggage limit is 62 linear inches. Always verify your specific airline's limits before traveling — they vary by carrier and route.
The formula
linear_inches = L + W + H (all in inches)
linear_cm = (L + W + H) × 2.54
Measure the full exterior dimensions including wheels, handles, and any protruding pockets. Airlines measure the bag fully extended.
Practical examples
Example 1 — Standard carry-on check
A rolling carry-on measures 22 × 14 × 9 inches:
22 + 14 + 9 = 45 linear inches (exactly at the common limit)
Example 2 — Soft-sided duffel (cm input)
Dimensions: 60 × 35 × 30 cm = (60 + 35 + 30) / 2.54 = 49.2 linear inches
This exceeds the 45-inch carry-on limit — must check or use as a personal item.
Example 3 — Checked bag near limit
Suitcase: 27 × 21 × 14 in = 62 linear inches — exactly at the standard checked limit.
27 + 21 + 14 = 62 linear inches ✓
Airline baggage size limits (indicative — verify with your airline)
Limits below are based on published policies as of 2026. Airlines update policies regularly.
| Category | Linear inches (typical) | Linear cm (typical) | Notes |
|---|---|---|---|
| Carry-on (most US/EU airlines) | 45 in | 114 cm | Common limit: 22 × 14 × 9 in |
| Standard checked bag | 62 in | 157 cm | Applies to economy on most carriers |
| Oversized checked bag | 63–80 in | 160–203 cm | Extra fees; limits vary by airline |
| Sports / special items | 80–115 in | 203–292 cm | Surfboards, bicycles — carrier-specific |
| Personal item (under-seat) | ≤ 36 in | ≤ 91 cm | Approx. 18 × 14 × 8 in typical |
Common mistakes
Not measuring handles and wheels. Most airlines measure the total external footprint of the bag, including extended handles and wheels. Retract handles fully when measuring, but include the wheel protrusion at the bottom.
Assuming all airlines use the same limit. While 45 linear inches for carry-on and 62 for checked bags are common, budget airlines, regional carriers, and premium carriers often have different limits. Always check the baggage policy page of your specific airline.
Confusing linear inches with any single dimension. "45-inch luggage" sometimes refers to a bag whose longest dimension is 45 inches — that is very different from 45 linear inches total. Read product listings carefully.
Quick reference — common bag sizes
| Bag type | Typical dimensions (in) | Linear inches | Fits as |
|---|---|---|---|
| Personal item / backpack | 18 × 14 × 8 | 40 | Under-seat |
| Cabin / carry-on | 22 × 14 × 9 | 45 | Overhead bin |
| Medium checked | 25 × 18 × 12 | 55 | Checked |
| Large checked | 27 × 21 × 14 | 62 | Checked (at limit) |
| Extra-large / duffel | 30 × 24 × 16 | 70 | Oversized / fees apply |
For clothing and shoe size conversions across US, UK, EU, Japan, and Australia in one page, see the International Clothing Size Chart →.