Why a lightweight parcel can cost more to ship
When sending clothes or household items to family overseas, the weight quoted at acceptance can exceed the weight shown on your scales.
Carriers can price the space occupied by a parcel using volumetric, or dimensional, weight.
A lightweight item in a large box may therefore attract a higher rate than its physical weight suggests.
This calculator compares actual and volumetric weight for each box, applies weight rounding, and looks up a per-box rate table.
Enter separate boxes in plan A and a combined or alternative packing arrangement in plan B.
Compare base postage, surcharges, additional fees and packaging costs before repacking.
The built-in tariff is specifically Korea-to-Japan non-document EMS postage, with all prices in KRW.
It does not estimate whole-house relocation costs or the tax-inclusive purchase price of imported goods.
Use the result to request a quote
Download the box dimensions and chargeable weights as CSV and show both plans to the carrier.
Compare the same contents, destination and service, including any repacking labor or materials.
A reduction in postage can be offset by additional packing costs.
Actual, volumetric and chargeable weight
Packed weight and outside dimensions
Actual weight includes the contents, carton, cushioning and tape.
Measure the outside of the finished parcel in cm, rather than the internal dimensions printed on a carton.
Bulging sides or a raised lid can increase the occupied space.
Dimensional and billable weight
Volumetric weight converts outside volume into kg using a divisor.
Chargeable weight uses the greater of actual and volumetric weight, then applies the minimum and rounding rules.
If the rate table has wider intervals, its selected rate-band limit can exceed the calculated chargeable weight; both are displayed separately.
Both plans must contain the same items, but their total packed weights can differ.
Combining parcels may remove a carton or require heavier protection.
The tool does not invent combined-box dimensions from the sum of existing volumes.
Enter the measured outside dimensions and packed weight of an arrangement you can actually prepare, or use dimensions supplied by the packing company.
Divisors and per-box rounding formulas
Volumetric weight V = length × width × height ÷ divisor
Comparison weight W = max(actual weight, V, minimum weight)
Custom chargeable weight = ceil(W ÷ increment) × increment
The Korea Post calculator publishes a divisor of 6,000 and compares actual with volumetric weight.
DHL Express guidance uses 5,000.
A smaller divisor produces a larger volumetric weight for the same box.
The divisor alone does not determine the bill: confirm the minimum weight, rounding and destination-specific rate table as well.
The custom carrier starts with editable settings of 5,000 and 0.5 kg; these are not guaranteed terms for every carrier or service.
Replace them with your quote conditions.
If the carrier requires each outside dimension to be rounded up to a whole cm, enable that option.
It rounds each side before multiplying, rather than rounding the resulting volume.
Do not combine weights before comparing them
A heavy compact box and a light bulky box can be charged on different bases.
Taking only the greater of total actual and total volumetric weight can understate a per-piece bill.
Rounding may also add weight separately to each box.
This calculator finds each box chargeable weight and base price first, then adds the results.
Scope of the built-in Japan EMS tariff
The built-in table is base postage for non-document EMS sent from Korea to Japan, checked against the official page on 2026-09-08.
Do not apply it to other countries, document services or EMS Premium.
A separate effective date was not established from the displayed table, so the date shown is a verification date, not an inferred commencement date.
Recheck the official tariff immediately before shipping.
Selected Korea-to-Japan non-document EMS base postage bands, excluding additional fees| Upper weight kg | Base postage KRW |
|---|
| 0.5 | 26,000 |
| 0.75 | 27,000 |
| 1 | 28,500 |
| 2 | 35,500 |
| 4 | 40,500 |
| 5 | 43,500 |
| 8 | 56,000 |
| 30 | 132,500 |
The calculation uses all 63 bands from 0.5 to 30 kg.
The minimum is 0.5 kg, with 0.25 kg intervals up to 2 kg and 0.5 kg intervals above 2 kg.
For example, 0.5001 kg moves to 0.75 kg, while 2.0001 kg moves to 2.5 kg.
A chargeable weight above 30 kg receives no extrapolated price and requires a separate quote.
A listed tariff does not establish acceptance of the dimensions or contents.
Include transport surcharges and packaging costs
The official base tariff excludes additional transport and handling fees.
Use the Korea Post estimated-charge lookup with the weight and dimensions of each packing plan to check the extras.
Fees can vary by destination, mail type, transport mode and weight, so an arbitrary average percentage can misrepresent the quote.
Enter the verified sum of weight-dependent extras separately for shipments A and B.
Total cost and avoiding double counting
For total base postage B, the percentage surcharge is round(B × surcharge percent ÷ 100).
Total cost = base postage + percentage surcharge + box count × per-box extra + shipment extra + packaging cost.
The percentage applies to base postage only, with one whole-KRW rounding at the aggregate surcharge.
If your contract applies a surcharge to other charges too, enter the verified amount in shipment extras instead.
Do not also enter pickup, insurance or handling fees per box if they are already included in the shipment extra.
Include cartons and cushioning in packaging cost and check what your packing service quote already covers.
An unconfirmed total does not mean free shipping.
The tool displays a total and cost difference only after rates and all extras are confirmed.
A verified zero extra is allowed.
Step-by-step input guide
- Match the contents of plans A and B and prepare the separate and alternative packages.
Each plan supports up to ten boxes; this is a software input limit, not a carrier acceptance limit.
- Measure the external dimensions and packed weight of each box.
Include protective materials and use the finished parcel rather than product-page measurements.
- For the custom carrier, enter the name, origin, destination, service and quote date.
Confirm the divisor, minimum weight, dimension rounding and weight increment before copying the per-box rate table.
- Enter one upper-kg,KRW-price pair per line, without thousands separators in the price.
Include all needed bands in increasing weight order.
Duplicate weights, decreasing prices, negative values or an empty table are not usable as a complete quote.
- Confirm each plan extra and packaging cost, then select the rate confirmation and same-contents checkboxes.
Changing dimensions or packed weights clears the confirmations because applicable fees may change.
- Review the per-box rows and total costs, then save the CSV.
Send the carrier the destination, service, shipping date and complete box list to obtain a final quote.
Worked separate-versus-combined example
A: two smaller boxes
Each box is 40 × 30 × 20 cm and weighs 2 kg.
EMS volumetric weight is 4 kg per box, giving 8 kg total chargeable weight.
Each 4 kg parcel costs KRW 40,500 in base postage, so the base total is KRW 81,000.
B: one combined box
A 40 × 30 × 40 cm box weighing 4 kg has 8 kg volumetric and chargeable weight.
Japan EMS base postage at 8 kg is KRW 56,000, a KRW 25,000 difference from A.
That is also the total-cost difference only under the explicit assumption of confirmed zero extras and packaging costs.
The total chargeable weight is identical but the base postage differs because two separate tariff lookups do not equal one lookup at the combined weight.
The outcome can reverse if the combined carton increases volumetric weight or incurs handling fees.
Check whether additional packing work costs more than the postage reduction.
A fictional custom rate table
With divisor 5,000 and a 0.5 kg increment, each A box moves from 4.8 to 5 kg, while B moves from 9.6 to 10 kg.
Using fictional rates of KRW 50,000 up to 5 kg and KRW 80,000 up to 10 kg, plus a 10% surcharge on base postage, A costs KRW 110,000 and B costs KRW 88,000.
These prices and the surcharge are test assumptions, not DHL or other carrier prices.
Interpret the results before changing the packaging
Cost attributable to volume compares the calculated amount with a hypothetical actual-weight-only price from the same table.
Minimum weight and rounding still apply, and only changes in base postage and its percentage surcharge are included.
It is not a separate surcharge appearing under that name on a carrier invoice, and it excludes changes in per-box extras or packaging cost.
In the EMS example, A would have KRW 71,000 base postage for two actual-weight-only 2 kg boxes, so the volumetric effect is KRW 10,000.
For B, the actual-weight-only 4 kg rate is KRW 40,500, producing a KRW 15,500 increase to KRW 56,000.
B has the larger volumetric increase but still has lower total base postage.
Use the full cost and adequate protection together, rather than selecting a plan from one indicator.
Useful household comparisons
- For clothes and bulky household items, measure an alternative package with less empty space.
- For books mixed with lightweight goods, inspect which boxes are actual-weight driven and which are volume driven.
- For fragile items, compare two adequately protected arrangements instead of removing cushioning solely to reduce cost.
- When sharing costs with family, share the verification date and unconfirmed items so everyone understands possible additional spending.
Frequently asked questions
Is combining boxes always cheaper?
No.
A larger carton may increase chargeable weight, handling fees or reinforcement costs.
Compare measured packing plans using actual quotes.
Can the packed weights of A and B differ?
Yes.
Identical contents can require different quantities of packaging.
Confirm the same items and include each plan packed weight and packaging cost.
Does the built-in table cover the United States or EMS Premium?
No.
It is only Korea-to-Japan non-document EMS.
Use the custom carrier section with the correct table, divisor and rounding rules for another service or destination.
Can I use a quote combining several boxes under one waybill?
This tool applies base postage per box.
A service charging once on the combined shipment weight has a different pricing scope.
Request a revised carrier quote instead of treating this total as applicable.
Can I enter only selected rows from a tariff?
The first upper limit covers every weight below it.
Missing intermediate bands are not recovered automatically, so enter all needed rows from the original table.
Weights above its maximum remain unpriced.
Why can I see base postage but no total?
A base tariff may be known while surcharges and extras remain unconfirmed.
The calculator separates these states and does not treat unconfirmed charges as zero.
Does saving the CSV book a shipment or contact the carrier?
No.
The CSV downloads the current inputs and results to your device.
Review it and use it yourself when requesting a quote.
Official sources and what to recheck
Sources were checked on 2026-09-08.
Review the tariff when base prices change and check transport surcharges against notices and the lookup at the time of shipment.
A price lookup alone does not confirm destination dimension limits, service suspensions, prohibited items or battery handling.
Customs duties, exemptions and insurance compensation are not calculated; verify declaration and contract terms separately.
Prepare the comparison before repacking
Start with matching contents, measured dimensions and verified rates in one comparison.
Enter the family-prepared boxes and the carrier-proposed alternative, then check for missing extras.
If the difference is small, consider packing effort, protection and handling convenience alongside price.
Obtain a final carrier quote before shipping.
Compare parcel packing plans