Linear dimensions: the measurement that decides everything
An airline does not care about your suitcase's volume. It cares about a single number, the linear dimension, which is length plus width plus depth added together. A case that is 28 × 18 × 12 inches has a linear size of 58 inches, and that 58 is the only figure the agent at the oversize belt compares against the limit.
The limit itself is one of the most consistent conventions in aviation: 62 inches, or 158 centimetres, for a checked bag, on essentially every major carrier in North America, Europe and Asia. Carry-on limits vary far more, but 45 inches / 115 cm is the figure most often quoted where a carrier states a linear carry-on limit at all. Because the checked limit is near-universal, luggage manufacturers design to it: a case advertised as a "large check-in" almost always lands between 60 and 62 inches linear so that it just clears.
Weight is the second gate, and it is separate. Economy checked bags are almost always capped at 50 lb / 23 kg, premium cabins commonly at 70 lb / 32 kg, and the two gates are tested independently. A bag can be perfectly sized and still overweight, or featherlight and still oversize. On most carriers you can be charged for both on the same bag, which is why a badly chosen case on a family trip can cost more than a seat.
The third multiplier is the one travellers forget: fees are charged per passenger, per paid segment. A $35 first bag on a round trip for two people is not $35 — it is $140 before anything has gone wrong.
How the fee total is assembled
Start with the geometry. Add your three measurements to get Dlin, and subtract that from the limit to get headroom. Positive headroom means the bag fits; negative headroom is the amount by which you are over, and no amount of repacking changes it, because a hard shell does not shrink.
Measure the way the airline measures. That means over the wheels, over any fixed feet, and over the housing that the telescopic handle retracts into. Manufacturers publish two sets of numbers — the interior packing dimensions and the true external dimensions — and only the second is relevant. If your case has an expansion zip and you have opened it, add the expansion to the depth.
Volume is the ordinary product L × W × H. To convert cubic inches to litres, divide by 61.0237, which follows from the exact definition of the inch: 1 in = 2.54 cm exactly, so 1 cubic inch = 2.54³ = 16.387064 cm³, and one litre is 1,000 cm³. Volume tells you nothing about whether the bag is legal, but it is the only fair way to compare two cases of different shapes for how much they actually hold.
The weight test is a strict inequality: you are overweight only when the packed weight exceeds the limit, not when it equals it. The amount to remove is the excess, and it is worth knowing precisely, because moving three pounds into a carry-on can be the difference between $0 and $100.
The fee side is a ladder rather than a rate. The first bag costs one amount, the second another, and every bag from the third up is normally a much higher flat charge — carriers price the third bag to discourage it, not to recover a cost. This calculator walks the ladder for each bag, adds an overweight and an oversize charge to every bag you flagged as matching the measured case, sums that into a per-passenger, per-segment figure, and multiplies by passengers and by paid segments.
Count segments carefully. A simple return trip is two segments. A connection on the same ticket is normally not a second charge, because your bag is checked through. Two separately ticketed flights on the same day are two charges even if you never leave the airport.
Worked example: two travellers, two bags each, one bag overweight
Take the default case: 28 × 18 × 12 inches, packed to 52 lb, on a carrier with a 62 in / 50 lb allowance, $35 for the first bag and $45 for the second, a $100 overweight fee and a $200 oversize fee. Two passengers, each checking two bags, on a round trip.
- Linear size. 28 + 18 + 12 = 58 in. Headroom is 62 − 58 = 4 in, so the bag is legally sized.
- Volume. 28 × 18 × 12 = 6,048 cu in. Divide by 61.0237: 99.1 L. That is a typical large check-in case.
- Weight test. 52 lb against a 50 lb limit, so the bag is over by 2 lb. Two pounds is a pair of shoes.
- Base fees per passenger. Bag 1 at $35 plus bag 2 at $45 = $80.
- Penalties per passenger. One bag matches the measured case, and it is overweight but not oversize, so $100 + $0 = $100.
- Per passenger, per segment. 80 + 100 = $180.
- Trip total. 180 × 2 passengers × 2 segments = $720.
Now move two pounds of shoes into a carry-on. The overweight fee vanishes on both the outbound and the return, for both travellers if both bags are trimmed: the per-passenger figure drops to $80, and the trip total falls from $720 to 80 × 2 × 2 = $320. Two pounds, $400 — and the reason is the two multipliers, not the fee itself. That is the single most valuable thing this page tells you.
How to read the headroom and the total
Headroom under about two inches is not a pass. Airport scales and belt gauges are not laboratory instruments, a soft-sided case bulges when it is full, and an expansion zip you opened at the hotel adds two inches of depth on the return leg. If your headroom is 1 in, treat the bag as marginal and expect to be measured on the day the flight is full.
Negative headroom is unfixable at the counter. Overweight can be solved by moving mass; oversize cannot, because the case's shell is the case's shell. If the linear figure is over, your options are to check a different bag, to pay, or — above roughly 115 in linear, where most carriers stop accepting checked baggage at all — to ship it as cargo.
Compare the total against the alternatives, not against zero. A $720 baggage bill for a family is in the same range as shipping a box ahead, buying a cabin-bag fare upgrade with a free checked allowance, or paying for a co-branded airline card that includes a free first bag for everyone on the reservation. This calculator gives you the number to compare; it does not know which of those is available to you.
Watch the third-bag cliff. The fee ladder is deliberately steep. In the fourth test scenario, four bags cost $35 + $45 + $150 + $150 = $380 in base fees alone — the last two bags cost more than four times the first. If you are near that line, redistributing weight across three bags is almost always cheaper than adding a fourth, even if it makes one of them overweight.
Volume is your shopping metric, linear size is your legal one. Between two 62-inch cases, the one with the more cubic shape holds more. A 62-inch bag proportioned 30 × 20 × 12 holds 7,200 cu in (118 L); one proportioned 34 × 18 × 10 also measures 62 in but holds 6,120 cu in (100 L). That is 6,120 ÷ 7,200 = 0.85, so 15% less capacity for the same legal footprint.
Common case sizes, their linear dimensions and their volume
| Typical case | L × W × D (in) | Linear (in) | Volume (L) | Headroom to 62 in |
|---|---|---|---|---|
| Underseat / personal item | 18 × 14 × 8 | 40 | 33.0 | +22 |
| Domestic carry-on | 22 × 14 × 9 | 45 | 45.4 | +17 |
| Carry-on, expanded | 22 × 14 × 11 | 47 | 55.5 | +15 |
| Medium check-in | 26 × 17 × 11 | 54 | 79.7 | +8 |
| Large check-in | 28 × 18 × 12 | 58 | 99.1 | +4 |
| Extra-large check-in | 31 × 20 × 13 | 64 | 132.1 | −2 |
| Cubic 62 in case | 30 × 20 × 12 | 62 | 118.0 | 0 |
| Long 62 in case | 34 × 18 × 10 | 62 | 100.3 | 0 |
The last two rows are the same legal size and differ by 100.3 ÷ 118.0 = 0.85, so 15% in capacity. Shape, not linear size, decides how much a compliant bag holds.
Fee schedules change, and this page does not know yours
Every fee field here defaults to a plausible figure, not to your airline's figure. Baggage charges move frequently, vary by route and cabin, differ between a bag paid online and one paid at the counter, and are waived entirely by many co-branded cards and elite tiers. Before you rely on the total, open your carrier's baggage page for your specific route and copy the four numbers in. The arithmetic on this page is exact; the inputs are only as good as your source.
The one figure you can generally take as given is the 62 in / 158 cm linear checked limit, which is stable across carriers and has been for decades.
Measuring and packing mistakes that cost money
- Measuring the shell, not the bag. Wheels, feet and the handle housing all count. A case that measures 60 in on the body can measure 63 in with its wheels, and the wheels are what the gauge touches.
- Trusting the manufacturer's marketing dimensions. Retail listings often quote interior packing dimensions. Measure the case yourself with a tape.
- Forgetting the expansion zip. Two inches of expansion turns a 60 in case into a 62 in case, and a 62 in case into an oversize one.
- Weighing an empty bag. An empty hard-shell spinner can be 10–12 lb on its own, so a 50 lb limit gives you under 40 lb of contents. Always weigh packed.
- Assuming oversize replaces overweight. On most carriers the two charges stack on the same bag. Breaking both limits at once is the expensive failure mode.
- Counting connections as segments. A bag checked through a connection is charged once for the whole ticketed direction. Two separate tickets are two charges.
- Splitting a heavy bag into a third bag. Because the third-bag fee is usually the steepest on the ladder, this often costs more than the overweight fee you were avoiding. Run both scenarios here before you decide.
When to use a different tool instead
This page prices bags you are taking on a flight. It is not the right tool for a whole relocation — if you are shipping a household rather than packing a suitcase, the moving boxes needed calculator works from room volume instead of linear dimensions, and the self-storage unit size calculator handles what does not travel with you.
Baggage fees are usually one line in a wider trip budget. The trip daily budget calculator puts them alongside accommodation and food, the hotel stay total cost calculator handles the resort fees and taxes that behave the same way, and the rental car total cost calculator covers the other airport charge that stacks multipliers on a headline rate.
If you are weighing a co-branded airline card against paying bag fees outright, price the card's free-bag benefit as a saving in the airline points and miles value calculator: a waived first bag for two passengers on two round trips a year is worth $280 at the default fee, which is often more than the card's annual fee on its own.
There is no single regulator setting baggage dimensions. The 62 in / 158 cm figure is a commercial convention that carriers adopted in common and that IATA resolutions on interline baggage helped standardise; weight limits of 23 kg and 32 kg trace partly to workplace manual-handling practice for the ground staff who lift them. Neither is law, and a charter or regional carrier is free to set something different — which is exactly why every limit on this page is an input rather than a constant.