One parcel or three: the arithmetic of splitting an order

Three shapes for one order: merged, split, or per-store

There are only three shapes an order can take. Everything merged into one build and one shipment, everything split into a small number of shipments, or every parcel shipped on its own. Each shape has a different lever, and the lever is what you actually choose when you choose a shape.

The merged shape pulls the volume lever and the waiting lever: it is cheapest per kilo and it holds the whole order behind the slowest seller. The split shape pulls the shipment-count lever, spending money to remove single-seller dependency. The per-store shape pulls the time lever and pays for it on every parcel separately.

The ladder this desk publishes prices all three at once using planning rates of 9.4, 13.8 and 21.5 per kilo and per-parcel fees of 1.5, 2.2 and 3.4. It also caps how many parcels travel in one shipment on each rung, and that cap is what decides whether a split is even available.

1. Merged shape: one build, up to six parcels, longest window, lowest planning rate.
2. Split shape: shipments of up to three parcels, middle rate, middle window.
3. Per-store shape: one parcel per shipment, highest rate, shortest window.
4. Cap first: parcel count against the cap decides which shapes exist for your order at all.

The merged build: best when nothing is urgent and nothing is fragile

The merged build is the default for a reason. It pays the per-kilo rate once on the whole chargeable weight and the per-parcel fee once on the whole order, which is the lowest planning total available, and it produces one border assessment instead of several.

Its cost is not money, it is dependency. One shipment means one build date, which means the slowest store sets the schedule for everything, and it means a single damaged carton affects the entire order. If any item in the order is a gift, a replacement for something broken, or tied to a date, the merged build is the wrong shape regardless of the arithmetic.

The merged build is also the shape that rewards packing work most, because its total is dominated by chargeable weight. Every kilogram of volume removed at the packing stage is multiplied by the lowest rate in the ladder, which is the cheapest kilogram you will ever remove.

1. Choose merged when no item has a date and no store is known to be slow.
2. Choose merged when the order is volume-heavy, because volume work pays best at the lowest rate.
3. Avoid merged when one item is irreplaceable, since a single carton is a single point of failure.

The two-shipment split: the middle rung and where it pays

The middle rung exists to break dependency without paying express rates. It holds up to three parcels per shipment, so an order of four to six parcels becomes two shipments instead of one, and the extra cost is one more handling fee plus one more border assessment on the same declared goods.

Where it pays is schedule. If one store in the order is slow, shipping the fast stores first removes the wait for most of the order at the price of one extra fee. Where it does not pay is a small order of two or three parcels, because the cap means those fit in a single shipment anyway and the middle rung then buys nothing except a higher per-kilo rate.

That is the most common mistake in this decision: choosing the middle rung for an order small enough to travel as one shipment, and paying the middle rate without receiving the split. Check the cap against your parcel count before you choose the rung, not after.

1. Split pays when parcel count exceeds the cap on the merged rung and one store is slow.
2. Split pays when a single late item would otherwise hold back a whole order.
3. Split does not pay below the cap, because the shipment count is the same and only the rate changed.
4. Split needs the extra border assessment counted, since each shipment is assessed separately.

The per-store build: what the marginal day actually costs

The fastest shape ships every parcel on its own, which pulls the window in from the weeks-long band of a merged build to a handful of days. It also pays the highest per-kilo rate and the per-parcel fee once for every parcel, so it is the only shape whose cost grows linearly with the number of stores you bought from.

The useful way to read it is as a price per day saved. On a fourteen kilogram order of five parcels, moving from the merged shape to the per-store shape changes the planning total from 133.1 to 318, and the front of the window moves from roughly three weeks to under a week. Whether that difference is worth paying is a question only the buyer can answer, but it should be answered with the number rather than with a feeling about speed.

The per-store shape has one non-obvious advantage: each parcel is assessed at the border on its own value, which can keep small parcels under a threshold that a merged carton would cross. On a threshold-sensitive order that effect can offset part of the extra cost, and it is worth calculating rather than assuming in either direction.

Marginal returns: the fourth parcel is not the third

Adding a parcel to an order costs more than the parcel. On a merged build it adds volume, which may or may not move the chargeable figure depending on which weight is driving it. On a split build it may push the parcel count past the cap and create a whole new shipment, which means another handling fee and another border assessment.

That step change is what people miss when they think in averages. The cost of the third parcel on a three-parcel order is not one third of the shipment cost; it is the cost of the shipment that already exists. The cost of the fourth parcel is a new shipment, which is why the marginal parcel is sometimes the most expensive one in the order.

The practical rule is to check the cap before adding anything, and to ask whether the new item could wait for the next order instead. Two orders of three parcels are usually cheaper than one order of six that crosses a cap, and the difference is a shipment you never paid for.

1. Check the cap before adding: the parcel that crosses it is the most expensive item in the order.
2. Check the driver before adding volume: if mass drives the figure, extra volume is free.
3. Check the threshold before merging: two small parcels may clear where one large one does not.
4. Check the next order: splitting across time is often cheaper than splitting across shipments.

Sizing the budget before you choose a shape

A budget cap is useful when it is set before the shapes are priced. Written first, it turns the ladder into a filter: any rung whose planning total exceeds the cap is rejected, and the decision becomes the cheapest shape that survives rather than a comparison of totals with no reference point.

Set the cap on the landed basis rather than the movement basis, and include the border lines and the extra handling that a split adds. A cap that only covers postage will be exceeded by the first split, and a cap that covers everything makes the trade-off visible: the gap between the cheapest surviving shape and the fastest one is the price of the schedule you want.

Then write the number down with the date. Bands get re-cut, rates get revised, and a cap that was correct last quarter is a historical document rather than a budget.

1. Set the cap before pricing, and include movement, handling and border lines in it.
2. Reject rungs against the cap rather than against each other, so the comparison has a fixed reference.
3. Keep the surviving cheapest shape and the fastest shape side by side, since the gap between them is the real decision.

The arithmetic on one worked order

The table below prices the same fourteen kilogram order of five parcels on all three shapes, using the published planning rates and per-parcel fees. All figures are on one scale, so only the ratios carry meaning, and a real quote can sit outside them in either direction.

Read the handling column first. It grows from 1.5 to 17 across the three shapes while the linehaul grows from 131.6 to 301, which means the fast shape pays a disproportionate share of its increase in fees rather than in transport. That is the signature of a split decision: what you are buying with the extra money is not speed in the air but the absence of waiting on the ground.

The data point behind this note

Own ladder rebuild, KB-2026-10: the three rungs were re-derived around shipment count rather than order value, publishing per-kilo planning rates of 9.4, 13.8 and 21.5 with per-parcel fees of 1.5, 2.2 and 3.4, and an over-cap flag so a rung can be rejected against a stated budget.

◇KB-2026-10· 2026-09-30 Batch ledger · Challenge a figure

Notes in the same cluster

Related entries and gauges

• How many shipments does your order actually need?
• How do you split an order across shipments without paying twice?
• Landed-cost ladder

  Three ways to move the same parcel, priced side by side.