The booking email goes out. The forwarder confirms a 40GP on next week's sailing. Warehouse starts building pallets — and halfway through stuffing, someone asks whether a 20ft would have been cheaper, or whether a 40HC would have fit two more pallet tiers.
That question belongs before the booking, not at the container door. Comparing two packing scenarios — different equipment sizes, stack patterns, or SKU mixes — takes twenty minutes in a calculator and saves the difference between optimal all-in per unit and shipping air at peak rates.
This guide walks through the scenario math importers and logistics managers use to compare load plans before committing equipment.
Why one scenario is never enough
Container booking is a capacity allocation decision disguised as a freight purchase. You are buying:
- Cube (CBM of usable space)
- Payload (kg of cargo budget)
- A freight stack (base ocean + surcharges + locals)
- Time (cutoff clocks and inventory exposure)
A single load plan answers "can we fit it?" Two scenarios answer "which box minimizes cost per unit shipped without breaching weight or stability limits."
Common pairs to compare:
| Scenario A | Scenario B | Question being tested |
|---|---|---|
| 20GP full | 40GP at same SKU mix | Does doubling space beat doubling-ish freight? |
| 40GP standard | 40HC | Does extra height add pallets without weight cap? |
| Dense stack (double-tier cartons) | Conservative stack (single tier) | Do crush limits force the less dense plan? |
| One 40GP | Two 20GPs | Weight-heavy cargo vs road limits |
| Current PO only | Current PO + next week's PO | Front-load vs split booking |
Step 1: Build both plans to the same standard
Apples-to-apples comparison requires the same rigor for each scenario:
- Same SKU list and quantities — unless you are explicitly testing a split-PO scenario.
- Same pallet type and dimensions — EUR vs GMA changes counts.
- Same dunnage allowance — void fill affects cube and weight.
- Same stability rules — heavy below, light above, door-end restraint.
- Documented utilization — cube % and payload % for each.
If Scenario B assumes "we'll double-stack the light cartons" but Scenario A does not, you are comparing packing strategy, not equipment size. That is valid — but label it clearly.
Step 2: Run the capacity math
Internal dimensions set the ceiling. Typical usable space (approximate):
| Equipment | Usable cube (CBM) | Typical payload (kg) |
|---|---|---|
| 20GP | ~28–30 CBM | ~28,000 |
| 40GP | ~58–60 CBM | ~26,500 |
| 40HC | ~68–70 CBM | ~26,300 |
For each scenario, record:
| Metric | Scenario A | Scenario B |
|---|---|---|
| Pallets loaded | ||
| Total pieces | ||
| Cube used (CBM) | ||
| Cube utilization (%) | ||
| Gross cargo weight (kg) | ||
| Payload utilization (%) | ||
| VGM estimate (kg) |
Winner on capacity is not always the larger box. A 40GP at 52% cube loses to a full 20GP on unit economics almost every time.
Step 3: Stack the freight numbers
Pull a quote or contract rate for each equipment type on the same sailing. Carriers rarely price 40ft at exactly 2× 20ft — typical ratios run 1.6–1.9× on many lanes, which is why 40ft wins when filled.
Illustrative transpacific spot (August 2026 — confirm your lane):
| Equipment | Spot all-in (ex duty) | Pallets | Cost per pallet | Cost per CBM |
|---|---|---|---|---|
| 20GP | $3,800 | 10 | $380 | ~$127 |
| 40GP | $5,900 | 21 | ~$281 | ~$102 |
| 40GP (same mix, only 16 pallets) | $5,900 | 16 | ~$369 | ~$133 |
The 40GP wins at 21 pallets but loses to the 20GP if you only load 16 — even though the cargo "fits" in the larger box.
Add surcharges explicitly:
- Base ocean
- BAF / EFS (confirm loading-date rules)
- THC origin and destination if not included
- Documentation and security
As of August 19, 2026. Not customs or legal advice. Duty sits outside the freight comparison but belongs in the landed-cost scenario if you are deciding whether to pull PO volume forward. Use a broker-confirmed rate; Palletizr stacks freight scenarios — it does not set duty percentages.
Step 4: Add landed-cost view (optional but powerful)
When tariff exposure is part of the booking decision, extend the table:
| Scenario | All-in freight | Units shipped | Freight per unit | Duty (broker rate) | Landed per unit |
|---|---|---|---|---|---|
| 20GP full — 10 pallets | $3,800 | 4,000 | $0.95 | + duty | $0.95 + duty |
| 40GP full — 21 pallets | $5,900 | 8,400 | ~$0.70 | + duty | ~$0.70 + duty |
| 40GP 65% — 14 pallets | $5,900 | 5,600 | ~$1.05 | + duty | ~$1.05 + duty |
Duty rate is constant per unit in this simplified view — but units per container changes, which changes how many containers you need for the same PO volume.
Step 5: Stress-test constraints
A scenario that wins on spreadsheet may fail on the floor. Check:
| Constraint | Pass / fail |
|---|---|
| Road weight limit on drayage route | |
| Crush limits on double-stacked cartons | |
| Door height — will pallets clear? | |
| Stability — voids, COG, door-end block | |
| VGM margin — within 5% of payload? | |
| Cutoff feasibility — can warehouse hit the plan? |
If Scenario B requires double-stacking that fails crush testing, discard it — even if cube math looks better.
Worked example: 20ft vs 40ft for mixed FMCG
Cargo: 18 EUR pallets of mixed cartons, ~420 kg per pallet, light enough to consider double-tier on some SKUs.
| 20GP (10 pallets max practical) | 40GP (18 pallets, single tier) | |
|---|---|---|
| Pallets | 10 | 18 |
| Cube util | ~88% | ~82% |
| Weight | ~4,400 kg | ~7,900 kg |
| Freight (illustrative) | $3,800 | $5,900 |
| Cost per pallet | $380 | ~$328 |
40GP wins on per-pallet freight — but requires two containers if the full PO is 18 pallets... or one 40GP if the PO fits. If the PO is only 10 pallets, the 20GP is correct. Scenario math prevents booking a 40ft "because it's cheaper per pallet" when you only have ten pallets to ship.
When to compare more than two scenarios
Add a third scenario when:
- 40HC might capture two extra pallet tiers for light freight.
- Split booking (20GP now + 20GP in two weeks) beats one under-filled 40GP.
- Front-loading the next PO changes pallet count enough to flip the equipment choice.
Three scenarios take slightly longer but still beat one rollover or one half-empty box at August spot levels.
Where Palletizr fits
Palletizr is built for this decision. Load the same SKU mix into two equipment profiles — compare cube %, pallet count, weight margin, and stack layout side by side. Export the winning plan to the warehouse and paste the utilization numbers into your booking request. The forwarder gets a serious booking; you get a defensible equipment choice.
Compare packing scenarios before you book at palletizr.com.
Bottom line
Do not book equipment on habit. Build two load plans, run capacity and freight math on cost per pallet and cost per CBM, stress-test weight and stability, and add duty only from broker-confirmed rates. The right container is the one that minimizes all-in cost per unit shipped — not the one that "usually works" for your category.