What the Cape of Good Hope diversion really costs your supply chain

The headline number is easy to quote: routing an Asia–Europe sailing around the Cape of Good Hope instead of through the Suez Canal adds roughly 10 to 14 days. Both the ITF/OECD analysis of the Red Sea crisis and UNCTAD's 2025 review put it in that range, alongside an increase of around 3,500 nautical miles per round trip and fuel consumption up by as much as 40 per cent.

That number is also the least useful part of the story. Ten to fourteen days is what it costs the carrier. What it costs you depends on decisions you made months earlier, and most of the damage lands somewhere other than the transit time.

Where the cost actually sits

Working capital

Every extra day at sea is a day your money is in a container rather than in your account. On a lane carrying £2m of goods a month, an extra twelve days of transit means roughly £800,000 of additional stock permanently in transit — not once, but continuously, for as long as the diversion lasts. That is working capital you have to fund.

Nothing on your profit and loss account shows this. It appears as a cash flow problem several weeks after the routing changed, usually described as a payables issue.

Safety stock, recalculated

Safety stock is sized against expected lead time and its variability. A diversion changes both: the mean goes up by twelve days, and the variance goes up too, because the new route is less familiar and more congested at the destination.

Teams that do not resize their buffers keep the old service level assumptions and quietly stop meeting them. Teams that do resize them discover the buffer has to grow by more than twelve days' cover, because it is the variability that drives the maths.

The promises you already made

This is the expensive one. Orders confirmed before the diversion carry dates calculated on the short route. Those dates are now wrong, and they were wrong the moment the carrier's routing changed — not when the container missed its ETA.

The gap between those two moments is where the relationship damage happens. A customer told in advance is managing a delay. A customer who finds out from a tracking page is managing a supplier problem, and they will remember it that way.

What the freight rate hides

Carriers price the longer route in, so the rate rises. But the rate is visible and gets attention, while the three costs above are invisible and do not. Teams routinely negotiate hard on a 20 per cent rate increase while absorbing a working-capital increase several times larger without discussion.

If you only track one number through a diversion, track days of inventory in transit rather than cost per container.

The decision that pays

The useful window is before carriers announce a diversion, not after. Insurance premiums and charter-market behaviour move first; routing announcements follow. In that gap, capacity on the alternative is available at normal rates and your customers have not yet been told a date you cannot meet.

Once the announcement arrives, everyone is bidding for the same alternative at once, and your customer has already read about it.

What to do this week

1. Work out which of your lanes cross Suez. Not which suppliers are "in Asia" — which specific lanes, because a supplier shipping from a different port may be unaffected.
2. Recalculate in-transit stock value at the longer transit time, and check it against your facility headroom.
3. Resize safety stock for the new mean and variance, not just the mean.
4. Identify orders already confirmed on pre-diversion dates and tell those customers now.

The first three are arithmetic. The fourth is the one that protects the relationship, and it is the only one with a deadline you do not control.