Cost Per Available Seat Mile Calculator

Work out cost per available seat mile instantly with clear inputs, formula shown and shareable results.

About Cost Per Available Seat Mile Calculator

Cost per available seat mile is total operating cost divided by seats times miles flown. Airlines quote it both including and excluding fuel, because fuel is volatile and outside management control while the ex-fuel figure reflects structural efficiency such as fleet choice, labour cost and utilisation.

Formula

Unit cost

CASM = operating cost / (seats x miles); ex-fuel CASM = CASM x (1 - fuel share)

Worked example

With the default values below, Cost Per Available Seat Mile Calculator returns Cost per available seat mile of $0.2099. Change any input above and every figure here is recalculated in your browser.

Inputs used

Operating cost for the sector: 34,000
Seats available: 180 seats
Sector distance: 900 mi
Fuel share of cost: 32 %

Results

Cost per available seat mile: $0.2099
Available seat miles: 162,000 ASM
Fuel element of CASM: $0.0672
CASM excluding fuel: $0.1427

Step by step

1Values used
2Unit cost
3Cost per available seat mile= 0.2099 per ASM
4Available seat miles= 162,000 ASM
5Fuel element of CASM= 0.0672 per ASM
6CASM excluding fuel= 0.1427 per ASM

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is CASM lower on long haul?

Fixed costs per departure — landing fees, ground handling, taxi fuel — are spread over many more miles, so unit cost falls with sector length.

How does seat density affect CASM?

Adding seats raises the denominator with little extra cost, which is the core of the low-cost carrier model.