Demurrage & detention calculator
Free, no sign-up. Enter the date the box became available, your contractual free days and the carrier’s per-diem tiers. The calculator applies weekend and port-holiday rules and returns a line-by-line breakdown you can share with the carrier. Versión en español.
Container timeline
Per-diem tiers
Leave the days field blank on the final tier so it covers every remaining day.
Breakdown
- Elapsed days
- 17
- Free time expires
- 2026-08-06
- Chargeable days
- 12
- Days excluded
- 0
| Days 1–5 · 5d × $150 | $750 |
| Days 6–10 · 5d × $250 | $1,250 |
| Day 11+ · 2d × $400 | $800 |
Think you were overbilled?
Most disputes are won on the clock anchor: carriers bill from discharge, but free time starts at availability. Send us the invoice and we run a blind audit — you pay only on recovery.
Run a free blind auditHow demurrage is calculated
Demurrage is billed per container per day for the time a full import box stays inside the terminal after free time expires. Detention covers the same idea outside the terminal — the days between pick-up and returning the empty. Both are tiered: the rate rises the longer the box is held.
The three variables that decide the number are the clock anchor, the free-day count basis and the closed-day rule. Anchoring on vessel discharge instead of availability commonly adds two to four billable days per container. Counting free time in calendar days when the tariff says working days adds one to two more.
Read the full explainer in demurrage vs detention, look up the free days your carrier grants at that port in the Free-Time Matrix, or check current dwell times on the Port Friction Index. Run a freight desk or publish trade content? Embed this calculator on your own site for free.