freightcalcsUSPS dimensional weight calculator
Divisor 139 in³/lb since 12 July 2026 — up from 166. Part of freightcalcs.com.
Divisor 139 in³/lb since 12 July 2026 — up from 166. Part of freightcalcs.com.
Rule change: USPS lowered its dimensional divisor from 166 to 139 effective 12 July 2026, filed with the Postal Regulatory Commission on 11 May 2026 (Docket CP2026-8). Any calculator or quote still using 166 will understate your billable weight by roughly 19%.
The new divisor applies to Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select. Crucially, USPS still only applies dimensional weight to packages larger than one cubic foot (1,728 in³) — below that threshold you are billed on actual weight no matter how light the parcel is. That single-cubic-foot exemption is what still separates USPS from FedEx and UPS, both of which dim-rate every package regardless of size.
A second change landed at the same time: fractional inches now round up rather than down.
Formula: L × W × H ÷ 139, but only when volume exceeds 1,728 in³ (28,316 cm³). Below that, billable = actual weight. Dimensions round up to the next whole inch.
Same 18 × 14 × 12 in box, 8 lb actual, shipped Priority Mail:
| Before 12 Jul 2026 | From 12 Jul 2026 | |
|---|---|---|
| Volume | 3,024 in³ | 3,024 in³ |
| Over 1 ft³? | Yes — dim applies | Yes — dim applies |
| Divisor | 166 | 139 |
| Dim weight | 18.2 lb → 19 lb | 21.8 lb → 22 lb |
| Billable | 19 lb | 22 lb |
Three extra billable pounds on an 8 lb shipment. Across a catalogue of bulky-but-light items the increase compounds — roughly 19% more billable weight on every dim-rated parcel.
This is the rule most shippers get wrong, and it is worth real money. USPS measures your package volume first:
| Package volume | How USPS bills |
|---|---|
| 1,728 in³ or less | Actual weight only — dim weight never applies |
| More than 1,728 in³ | Greater of actual weight and volume ÷ 139 |
A 12 × 12 × 12 in cube is exactly 1,728 in³ and stays on actual weight. Add one inch to any side and the whole package becomes dim-rated. If your carton sits just over the line, dropping below one cubic foot is the single highest-value packaging change you can make — it is a cliff, not a slope. Use the cube utilization page to find the slack.
On 12 July 2026. USPS filed the change with the Postal Regulatory Commission on 11 May 2026 under Docket CP2026-8, moving from 166 to 139 to align with the divisor FedEx and UPS have used for years.
No. USPS only applies dimensional weight to packages larger than one cubic foot — 1,728 cubic inches. Anything at or below that volume is billed on actual weight, however light it is. This exemption survived the July 2026 change.
Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select. First-Class-type letter and flat products are not dimensionally rated, and Flat Rate boxes are priced by box, not weight, so dim weight is irrelevant to them.
On a package that was already dim-rated, billable weight rises about 19% — the ratio of 166 to 139. The dollar impact depends on your zone and service. Packages under one cubic foot are unaffected.
Up. Alongside the divisor change, USPS switched to rounding fractional inches up to the next whole inch before calculating volume. Previously fractions were rounded down, which quietly favoured the shipper.
No. Flat Rate pricing is by container, not by weight, so the divisor is irrelevant. For bulky low-density items that fit, Flat Rate is often the cheaper answer precisely because it sidesteps dim weight entirely.
FedEx · UPS · DHL Express · Amazon (FBA & Buy Shipping) · Canada Post · Australia Post · Purolator · Parcelforce · TNT
Compare all carrier divisors · Chargeable weight · CBM calculator · Weight or measure