What Demurrage and Detention Actually Cost Kenyan Importers: We Did the Math

Reading time: 7 minutes

Your container cleared customs on Tuesday. Nobody told you it had already started costing you money on Friday.

That's not a typo. That's how demurrage and detention actually work — and it's why so many logistics managers and freight forwarders only discover the charge when the invoice lands, weeks after the cargo has already moved on. By then, there's nothing to negotiate. The clock already ran out.

We looked at how this actually plays out across Mombasa, Dar es Salaam, and the carriers that move through them. Here's what we found.

The Two Clocks Nobody Is Watching

Most logistics professionals talk about "free days" as if it's one number. It isn't. It's two separate clocks, run by two separate parties, and they don't start or stop at the same time.

The port's clock (demurrage): Charged by the terminal for the container sitting in the yard past its free period, before you collect it.

The carrier's clock (detention): Charged by the shipping line for the container itself — the steel box — being held outside the port past its free period, before you return it empty to the depot.

Two clocks. Two different durations. Two different parties charging you. And nothing on a standard shipping instruction tells you where either one currently stands.

The average container dwell time at the Port of Mombasa is roughly 97 hours — just under 4 days. That sounds comfortable against a 5-day free window. But that's an average. Half of all shipments take longer. And the moment a single missing signature or a misrouted email adds two more days, the gap between "fine" and "billable" closes without anyone noticing.

The Math

Take a logistics manager moving 80 shipments a month — a fairly typical mid-sized importer.

If roughly 20% of those containers slip past the port's free window by an average of 3 days, at a standard demurrage rate of $60–70/day:

16 shipments/month × 3 days × $65/day = $3,120/month in demurrage alone

Add detention. If 10% of containers are also held past the carrier's free window by an average of 2 days:

8 shipments/month × 2 days × $70/day = $1,120/month in detention

Combined: roughly $4,240 a month — over $50,000 a year — in charges nobody budgeted for, on a single mid-sized operation.

Multiply that across every importer and forwarder moving cargo through Mombasa and Dar, and the regional number runs into the tens of millions annually. None of it shows up as a line item until the invoice does.

Why This Keeps Happening

It isn't carelessness. It's structure.

1. Free-day tracking is manual, and the volume doesn't allow it. A logistics manager running 80 shipments a month would need to mentally track up to 160 separate countdowns — two per container — on top of everything else they're coordinating that day. Nobody does that reliably with a notebook and a phone.
2. The two clocks have different rules at every port and every carrier. Mombasa's 5 days isn't Dar's 4. Maersk's 14 isn't Evergreen's 7. A forwarder working multiple corridors and multiple shipping lines is juggling a different rulebook for every shipment — and there's no single system reconciling them.
3. Nobody finds out until it's too late to act. Demurrage and detention invoices typically arrive weeks after the charge was incurred, often bundled into a final account that's already disputed line by line. By the time you see the number, the window to avoid it closed a long time ago.

This is the same root problem behind the empty-miles crisis: information that exists, but isn't visible to the person who needs it, at the moment they need it.

How We Built It

D&D Monitoring on Logistics & Beyond tracks both clocks — port and carrier — automatically, for every container on the platform. It uses the actual local defaults: Mombasa's 5 days, not a generic assumption; Maersk's 14, not a rounded estimate. The moment a shipping instruction is created, both countdowns start, and you get notified well before either one closes — not after.

It's free on every plan. We're not selling you a way to find out what you owe. We're giving you a way to make sure you never owe it.

If demurrage and detention charges have shown up on an invoice you didn't see coming, this is exactly the problem we built the platform to solve.

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