Dimensional Weight Calculator
Parcel DIM and billable weight in imperial and metric.
What it does
Carriers charge by weight or by size, whichever costs them more. A box of pillows weighs little but fills a truck, so the invoice follows its volume. Dimensional weight turns size into pounds or kilograms so the two can be compared head to head.
The tool above does the comparison. Enter the packed box size and its scale weight, and it prints the DIM weight, the billable weight, and which one rules. The default 18 by 12 by 12 in box at 10 lb gives 15.6 lb DIM, so the bill is 15.6 lb billable. The metric mirror at 46 by 30 by 30 cm and 4.5 kg gives 6.9 kg DIM and 6.9 kg billable, the same physical parcel in other units.
The divisors look arbitrary but encode one density line. US parcel practice divides cubic inches by 166, while air cargo divides cubic centimeters by 6000. Both draw the line at the same fluffiness: below it you pay actual weight, above it you pay for the space. Small parcels under about one cubic foot often skip DIM on some services, but the trend is toward wider use.
This page uses outer packed dimensions and scale weight. It does not include carrier rounding, fuel surcharges, zone pricing, or service specific cutoffs. Always confirm the tariff for the exact service before quoting a customer.
How to use
- Pick imperial (in, lb) or metric (cm, kg).
- Measure the outside of the packed box: length, width, height.
- Weigh the packed box on a scale.
- Read DIM weight first, then billable weight.
- Check the basis line to see which weight rules.
- If DIM rules, try a smaller box or split the shipment.
Formula
- L, W, H
- Box length, width, height in inches for imperial, in cm for metric.
- actual
- Scale weight of contents plus box, in lb or kg.
- divisor
- Cubic inches per pound (166) or cubic cm per kg (6000).
Divisors 166 and 6000 describe the same density line in different units. Carriers apply DIM mainly above one cubic foot and round dimensions and weights up; exact rounding follows the service tariff.
Worked example
Example: 18 by 12 by 12 in box at 10 lb
Defaults: imperial 18 by 12 by 12 in with 10 lb actual. Metric mirror is 46 by 30 by 30 cm with 4.5 kg.
- Inputs (imperial default): 18 by 12 by 12 in, actual 10 lb.
- Volume: 18 times 12 times 12 is 2,592 cubic in.
- DIM: 2,592 / 166 is 15.6 lb DIM.
- Billable: larger of 10 and 15.6 is 15.6 lb billable.
- Basis is DIM weight applies. Metric mirror (46 by 30 by 30 cm, 4.5 kg) gives 6.9 kg DIM and 6.9 kg billable.
Reference table
| Parcel | DIM | Billable |
|---|---|---|
| 18 by 12 by 12 in, 10 lb | 15.6 lb DIM | 15.6 lb billable |
| 12 by 10 by 8 in, 5 lb | 5.8 lb DIM | 5.8 lb billable |
| 46 by 30 by 30 cm, 4.5 kg | 6.9 kg DIM | 6.9 kg billable |
| 50 by 40 by 30 cm, 8 kg | 10 kg DIM | 10 kg billable |
| 10 by 8 by 6 in, 9 lb | 2.9 lb DIM | 9 lb billable |
Limits
- Outer packed size only. Fillers and double walls count.
- No carrier rounding or zone rates. Tariffs round up first.
- Service cutoffs differ. Some small parcels skip DIM.
- Density line only. Fragile and oversize fees are extra.
Common mistakes
- Measuring the product instead of the packed box.
- Forgetting the box and tape weight on the scale.
- Mixing inches with the 6000 divisor, or cm with 166.
- Assuming one divisor fits every carrier and service.
- Shipping air in an oversize box and paying for empty space.
Try it yourself
Quick checks. Answers sit tucked under each question.
12 by 10 by 8 in, actual 5 lb?
Volume is 12 times 10 times 8 is 960. DIM is 960 / 166 is 5.8 lb DIM, over 5 lb actual, so 5.8 lb billable.
50 by 40 by 30 cm, actual 8 kg?
Volume is 50 times 40 times 30 is 60,000. DIM is 60,000 / 6000 is 10 kg DIM, over 8 kg actual, so 10 kg billable.
Questions
How is dimensional weight figured?
DIM is length times width times height / 166 in pounds, or / 6000 in kilograms. Here 2,592 / 166 is 15.6 lb DIM.
Which weight does the carrier bill?
The larger of actual and DIM. Here max of 10 and 15.6 is 15.6 lb billable.
Why 166 and 6000?
166 cubic in per lb matches 6000 cubic cm per kg. Both describe the same density cut between bulky and dense.
Does DIM apply to tiny parcels?
No. DIM applies above one cubic foot (1,728 cubic in) on many services. Below that, actual weight rules.
Do I round dimensions first?
Round each side as the carrier asks, often up to the whole inch. Rounding up first can flip the basis.
How do I cut a DIM charge?
Split the order or pick a smaller box. DIM falls with volume while actual stays put.