How to compare carriers for one parcel using your own rates

Carrier rate tables are long, change often and depend on your account, so the reliable way to compare carriers is to use the rates you were actually quoted. This guide shows a simple spreadsheet method that gives an estimate of cost per parcel on each carrier. It does not need any special software.

Before you start

• Collect your own rates: the price per weight and zone from your account, your reseller's rate card, or the retail rate chart the carrier publishes. Note the date and which service each column applies to.
• Know each carrier's divisor and rounding (our guide "How to measure a parcel and work out its dimensional weight" walks through the arithmetic). Note that some carriers only apply dimensional weight above a size threshold.
• Pick two or three typical parcels and the zones you ship to most.

Set up the sheet

1. One row per parcel: length, width, height, actual weight in lb.
2. Columns for rounded dimensions: =ROUNDUP(B2,0) for each side (if the carrier rounds up).
3. A volume column: the three rounded sides multiplied.
4. For each carrier, a DIM weight column: =ROUNDUP(volume/divisor,0). For a carrier that only applies DIM above a threshold, wrap it: =IF(volume>1728,ROUNDUP(volume/139,0),0).
5. A billable weight column per carrier: =MAX(ROUNDUP(actual,0),dim). If the carrier prices fractions of a pound differently, adjust to its rule.
6. A price column per carrier: look up the billable weight and zone in your rate table with VLOOKUP or INDEX/MATCH.
7. Add any surcharge you know applies (for example fuel or oversize), from the same dated source.

Read the result carefully

• The cheapest carrier for a 1 lb box is often not the cheapest for a bulky 5 lb box. Compare several parcel types, not one.
• If two carriers are within a small amount, the difference is within the error of an estimate. Delivery speed and tracking may decide it.
• Re-check against actual invoices after a few shipments and adjust the sheet.

A calculation like this is an estimate of postage only. It does not cover taxes, duties, customs or insurance, and it is not tax, customs or legal advice. Dimloom does the same comparison in your browser: you type or paste your own rate table, nothing is sent to us, and the results are labelled as estimates.

Sources

1. USPS, Domestic Mail Manual 283, section 1.4 (threshold, divisor and rounding): https://pe.usps.com/cpim/ftp/manuals/dmm300/283.pdf (read 2026-10-27)
2. UPS, "Shipping dimensions and weight": https://www.ups.com/us/en/support/shipping-support/shipping-dimensions-weight (read 2026-10-27 as a search-index excerpt; ups.com blocks automated fetching)
3. FedEx, "What is dimensional weight?": https://www.fedex.com/en-us/shipping/packaging/what-is-dimensional-weight.html (read 2026-10-27)

Related tool: Dimloom. Estimates and guidance only; check the source documents before relying on a figure.

More Dimloom guides

• How to measure a parcel and work out its dimensional weight
• USPS Ground Advantage dimensional weight: the 139 divisor and the 1 cubic foot rule
• UPS and FedEx billable weight: how the rules differ

All guides