Enter your carrier's free time and rate tiers, and the actual days used, to calculate detention and demurrage charges — including escalating tiers, not just a flat daily fee.
Demurrage is charged for a container sitting at the port or terminal past its free time, before it's picked up. Detention is charged for a container that's been picked up but not returned (empty, or at the export terminal for loading) past its own free time. They have separate free-time allowances and often separate rate schedules, which is why this tool calculates them separately.
Free time and per-diem rates are set carrier by carrier, often lane by lane and contract by contract, and are commonly structured as escalating tiers rather than one flat rate — a rate that applied on one shipment may not apply to another with the same carrier. Your own tariff or service contract is the only reliable source; this tool does the arithmetic once you have it.
Carriers use escalating tiers specifically to discourage long container dwell times — the longer a container sits, the more it costs per day, not just in total. A flat per-diem doesn't create that same pressure to return equipment quickly.
Your carrier's published tariff (often on their website), your service contract if you have one, or your freight forwarder can provide the specific free time and per-diem schedule that applies to your shipment and trade lane.
No — free time counting rules (calendar days vs. working days, and how holidays are treated) vary by carrier and port. Use whatever day count your carrier's own terms specify as "free days" and "actual days used."
Yes. A container can accrue demurrage while waiting at the terminal, then detention after it's picked up but before it's returned — both charges independently possible on the same move, which is why they're calculated separately here.
The terms and tiered-rate structure are most common in ocean freight container moves, but the same escalating-tier arithmetic applies to rail and some trucking demurrage/detention schemes — enter whatever free time and tiers your specific contract uses.
No. It calculates what the charge should be based on the free time and tiers you enter, so you can compare that to what was actually invoiced — the comparison itself, and any dispute, is between you and your carrier.
This calculator checks one invoice at a time. Mirage checks every carrier invoice against your contracted rates and free-time terms automatically, before payment.
See Freight Invoice Audit