Starting August 18, 2025, FedEx and UPS will round every fractional inch up when measuring length, width, and height for dimensional (DIM) weight. Example: 11.1″ becomes 12″; 8.01″ becomes 9″. FedEx confirms the new rounding in its 2025 rate updates; UPS has matched the policy beginning the same date. More cubic inches means higher billable weights and more surcharge trips. This article breaks down what’s changing, who’s hit hardest, and the ways to protect margin.

What is DIM weight?

Dimensional (DIM) weight prices a parcel by the space it occupies as well as its scale weight. Carriers compute a volumetric weight from the box size and charge the greater of actual weight vs. DIM weight.

Formula (U.S. inches):
DIM weight (lb) = ⌈(Length × Width × Height) ÷ divisor⌉

Common divisors: 139 (many negotiated/daily accounts) and 166 (some retail/counter accounts). Your contract controls the exact value.
After DIM is computed, carriers round up to the next whole pound and compare to actual weight.

Example:
Box 12 × 9 × 7 in → volume 756 in³

With divisor 139: 756 ÷ 139 = 5.44 lb → 6 lb DIM
If actual weight = 4.2 lb, billed weight = 6 lb (DIM wins).
If actual weight = 7.0 lb, billed weight = 7 lb (actual wins).

Why carriers use it: Light, bulky parcels (pillows, apparel, void-filled boxes) consume vehicle space; DIM weight aligns price with space usage, not just mass.

What is the DIM Rounding Rule?

Effective August 18, 2025 (FedEx and UPS), any fractional measurement of length, width, or height is rounded up to the next whole unit before applying the DIM formula.

Example: 11.1″ → 12″, 8.01″ → 9″.
This increases cubic volume used in the calculation, which can raise billable weight and push more shipments over dimension-based surcharge thresholds (e.g., >48″ longest side, >30″ second-longest side).
The usual post-calculation step still applies: billed weight is rounded up to the next whole pound after DIM is computed.

What exactly is changing with new FedEx & UPS DIM Rounding Rule?

New rounding rule: any fraction of an inch (or centimeter) rounds up to the next whole number before DIM is calculated—for both carriers.
Additional-handling thresholds stay the same, but the stricter rounding means more parcels will cross them (e.g., longest side > 48″ or second-longest side > 30″ at UPS). UPS

FedEx statement: “FedEx will round every fraction of an inch/centimeter up to the next-higher inch/centimeter.” FedEx

Why does new FedEx & UPS DIM Rounding Rule matter?

DIM weight grows because rounding up increases cubic inches before the divisor is applied. Billable weight is the greater of actual vs. DIM. (Divisors vary by carrier/account; consult your agreement.) Shopify
Example of a common bump: a box measured at 11.1 × 8.5 × 6.2″ now rounds to 12 × 9 × 7″, which can push a shipment from ~5 lb to ~6 lb (≈ +20% billed weight before fees).
More surcharges get triggered: Rounding can tip dimensions over thresholds such as UPS Additional Handling (>48″ longest side or >30″ second-longest side). FedEx’s Additional Handling – Dimension can also apply—and when it does, FedEx enforces a 40-lb minimum billable weight on the package.

FedEx example (Rounding + 40-lb minimum under AHS–Dimension)

Measured: 48.1 × 12.0 × 6.0″ at 10 lb
New rounding: 49 × 12 × 6″ (48.1 → 49)
DIM divisor: FedEx uses a divisor per account/service; for illustration, 139.
- DIM = (49×12×6) / 139 = 25.38 lb → 26 lb billed
But the package’s longest side > 48″, so Additional Handling – Dimension applies. Under FedEx’s 2025 Service Guide, rating is subject to a 40-lb minimum billable weight when AHS–Dimension criteria are met.
Final billable weight: 40 lb, not 26 lb. FedEx

Why costs jump: that tiny 0.1″ overage now rounds to 49″, crossing the 48″ threshold and invoking a 40-lb minimum.

References: FedEx 2025 Rate Changes and FedEx 2025 Service Guide (non-standard shipment & AHS details).

UPS example (Rounding + Additional Handling thresholds)

Measured: 48.1 × 12.4 × 8.2″ at 8 lb
New rounding: 49 × 13 × 9″ (each fraction rounds up)
UPS Daily illustration with divisor 139: DIM = (49×13×9)/139 = 41.24 lb → 42 lb billed
UPS Retail/counter illustration with divisor 166: DIM = 34.54 lb → 35 lb billed
Impact: Longest side > 48″ ⇒ Additional Handling likely applies (adds a surcharge). Unlike FedEx, UPS does not impose a 40-lb minimum billable weight specifically for AHS—your charged weight remains the greater of actual vs. DIM.

Reference: UPS page on avoiding additional fees (includes >48″ and >30″ thresholds); press coverage confirming round-up of any fraction beginning Aug 18, 2025

What to do after new FedEx & UPS DIM Rounding Rule take in affect?

Use this checklist to cut DIM weight and avoid surcharge triggers fast. It’s written for ops teams using Shopify, a WMS/OMS, and shipping with FedEx and UPS.

Audit & measure (first 48 hours)

Pull last 60–90 days of parcels (dims, actual weight, service, zone, surcharges).
Plot dims around whole-inch thresholds (12, 18, 24, 30, 48). Look for spikes at x.1–x.9″ that will now round up.
Identify SKUs with low density (cubic inches per pound high) — prime DIM risk.
Flag all parcels where longest side ≥ 47.9″ or second-longest side ≥ 29.9″ (AHS tripwires).

Right-size packaging (engineering quick wins)

Prune carton sizes; eliminate overlaps. Add multi-depth cartons and on-demand or scored boxes to hit whole-inch targets.
Swap boxes for poly/bubble mailers where protection allows. Use inserts to reduce void.
Standardize pack-outs for top SKUs so finished dims land at whole inches (e.g., 12.0″, 18.0″, 30.0″, 48.0″).
Set a “no air” rule of thumb (e.g., void ≤ 10%) and enforce with random checks.

WMS/OMS cartonization rules (prevent surprises)

Update cartonization to target whole-inch cutoffs (e.g., never finish at 48.1″).
Encode rules that prefer cartons keeping the second-longest side ≤ 30.0″ and longest side ≤ 48.0″ when possible.
Refresh DIM tables and service maps per carrier; separate logic for UPS Daily (139) vs UPS Retail (166) if you use both.

Pack stations & measurement SOPs (process control)

Calibrate dimensioners and scales (daily quick check + weekly full check). Document tolerances.
Provide rigid rulers/gauges marked at common thresholds (12/18/24/30/48).
Train on the new rounding rule and post a 1-page visual: “any fraction rounds up.”
Add a packout sign-off for at-risk SKUs (spot-check dims before sealing).

Model by lane & carrier (decision support)

For each top SKU/carton: compute pre- vs post-rounding DIM, then compare FedEx vs UPS billable weight.
Watch for threshold trips: >48″ longest, >30″ second-longest (AHS risk) and service-specific limits.
Maintain two calculators:
- UPS Daily (139) vs UPS Retail (166) paths.
- FedEx DIM plus AHS–Dimension scenarios (minimum billable weight risk when AHS is triggered).
Choose services/boxes that keep you under thresholds while minimizing DIM weight.

Carrier strategy & contracts (protect the P&L)

Ask reps about AHS definitions, waivers/caps, and any DIM divisor improvements for key lanes.
Re-test Ground Economy/Ground Saver vs standard Ground after rounding; the winner can change by SKU/zone.
Track hit rate of AHS by carrier and use the data in negotiations.

Pricing & CX alignment (no profit leaks)

Align promotions and free-ship logic with post-rounding costs (consider tiered thresholds by category/size).
Offer pickup/BOPIS or consolidated shipping for bulky items to avoid DIM shocks.
Update returns packaging guidance so customers don’t incur oversize charges on the way back.

KPIs & governance (keep it sticky)

Dashboard weekly: DIM % of orders, AHS rate, avg billed weight vs actual, $ per order, margin impact.
Run A/B pack-outs for top 10 SKUs to validate savings.
Add DIM checks to new-SKU onboarding so packaging decisions bake in whole-inch targets from day one.

Conclusion

Effective August 18, 2025, the “round any fractional inch up” rule increases the cubic inches used in DIM calculations. As a result, more parcels—especially light or bulky ones—will rate at higher billable weights and are more likely to cross Additional Handling thresholds (e.g., >48″ longest side, >30″ second-longest side). The impact varies by SKU mix, packaging, and service. Quantify it by modeling your top SKUs and lanes with the new rounding, your current DIM divisors (e.g., 139/166), and each carrier’s AHS logic. Mitigation should focus on: (1) right-sizing packaging, (2) cartonization rules that target whole-inch cutoffs, (3) calibrated measurement SOPs at pack stations, and (4) carrier/contract reviews where thresholds or surcharges drive outsized costs.

Jay Group can run a rapid DIM-impact audit and model pre- vs. post-rounding billed weights, powered by Manhattan WMS and Qlik Sense BI . We also capture exact box dimensions at pack-out and feed them into a custom box machine to right-size packaging and avoid 48.1″ pitfalls. When it makes sense, we optimize the carrier mix and leverage bi-coastal facilities (PA & NV) to reduce zones and soften DIM inflation.

FAQ: DIM Weight, Rounding, and Surcharges (2025)

What is dimensional (DIM) weight?

DIM weight prices a parcel by the space it occupies rather than scale weight alone. Formula (inches):
DIM (lb) = ⌈(L × W × H) ÷ divisor⌉, where L/W/H are measured after rounding each side up to the next whole inch. Carriers bill the greater of actual vs. DIM weight.

What changed on August 18, 2025?

FedEx and UPS now round any fractional inch up for length, width, and height before calculating DIM. Example: 11.1″ → 12″. This increases cubic inches and raises billable weight—especially for light, bulky SKUs.

What is the DIM divisor (139 vs. 166), and which one do I use?

The divisor converts volume to a billable weight. Common paths:

UPS Daily/negotiated accounts: often 139
UPS Retail/counter/Store: often 166
FedEx: divisor depends on your contract/service.
Check your rate guide or contract; the divisor can differ by service and account.

How does rounding affect my costs?

Rounding each side up increases the cubic inches, so the DIM figure rises. Since carriers bill the greater of DIM vs. actual, more packages price at higher billed weights. Rounding also pushes more shipments over surcharge thresholds.

What are UPS Additional Handling thresholds (and why do they matter)?

Common dimension triggers include longest side > 48″ or second-longest side > 30″. The new rounding makes it easier to cross those limits (e.g., 48.1″ → 49″), adding Additional Handling (AHS) fees even if the pre-rounded measure looked safe.

What is FedEx Additional Handling – Dimension, and what is the “40-lb minimum”?

If a FedEx package meets AHS – Dimension criteria (e.g., exceeds a dimension threshold), it can be rated at a minimum billable weight (e.g., 40 lb) even if its DIM/actual is lower. Rounding a side from 48.1″ → 49″ can trigger AHS and that minimum, significantly raising cost.

How do I reduce DIM weight and avoid surcharges?

Right-size packaging; eliminate void fill.
Target whole-inch cutoffs (e.g., keep 47.9″ within 48.0″, avoid 48.1″).
Re-cartonize in WMS/OMS to choose cartons that stay under >48″ / >30″ thresholds.
Calibrate dimensioners; train packers on the “any fraction rounds up” rule.

What is cartonization (and why does it matter for DIM)?

Cartonization is the logic your WMS/OMS uses to pick the best-fit carton for each order. Good rules minimize cubic inches and avoid threshold trips. Update rules to:

Prefer cartons that keep longest side ≤ 48.0″ and second-longest ≤ 30.0″
Land finished pack-outs on whole inches (12.0, 18.0, 24.0, 30.0, 48.0)
Consider multi-depth or on-demand boxes for flexibility

How should I set up Shopify to reflect the new DIM rounding?

Audit Product dimensions (no stale vendor guesses).
Use Shipping Profiles and rules/apps that reference your actual divisor and round-up behavior.
Tune free-shipping thresholds for bulky categories to protect margin.
Ensure any live-rate calculator reflects 139 vs. 166 where applicable.

Does the rounding rule apply to all FedEx/UPS services (Ground, Ground Economy/Saver, Air)?

Rounding affects how dimensions are measured wherever DIM applies. Service-specific divisors, surcharges, and exclusions still depend on your agreement. Always check your service guide for exceptions.

What about international shipments (centimeters)?

The rounding concept is the same—any fractional centimeter rounds up. Divisors/volumetric factors can differ by service and region. Confirm your international tariff before modeling.

How do I calculate the true impact on my SKUs?

Build a quick model:

Round each side up to the next whole inch (or cm).
Compute DIM = volume ÷ divisor; round up to the next lb.
Billable weight = max(actual, DIM).
Check for AHS triggers (>48″, >30″, etc.) and apply any minimum billable weight rules (e.g., FedEx AHS–Dimension).
Compare pre- vs. post-rounding by lane/carrier.

Is billed weight always rounded up to a whole pound?

Yes—after you compute DIM, carriers round up to the next whole lb and then compare to actual weight.

What if my dimensioner shows 11.00″ sometimes and 11.05″ other times?

Implement SOPs and calibration. Small drifts now matter: 11.05″ → 12″ under the new rule. Add hard rulers/gauges at pack stations and run daily spot checks.

Are USPS rates affected by this change?

This update is specific to FedEx and UPS. USPS has its own dimensional rules and thresholds; review the current USPS guide separately if you ship with them.

What KPIs should I track after the Aug 18, 2025 change?

DIM as % of orders
AHS hit rate (by carrier and threshold)
Avg billed vs. actual weight
Surcharge $ per order
Margin impact by SKU/lane
Use these to guide carton set updates, WMS rules, and carrier negotiations.

Will negotiating the DIM divisor help?

Potentially. Some shippers secure a more favorable divisor or caps/waivers on AHS via contract reviews. Bring data: show where rounding pushes you over 48″/30″ and quantify the cost.

Can poly mailers or flats help reduce DIM weight?

Yes—mailers often reduce cubic inches vs. boxes (when product protection allows). Test durability and returns experience. For boxes, consider scored or multi-depth designs to land on whole-inch targets.

How do I “what-if” test before peak season?

Take your top 20 SKUs, apply the round-up to current pack-outs, compute DIM with your divisors, then run FedEx vs. UPS and service-by-service comparisons. Flag any that cross >48″ or >30″ after rounding; redesign pack-outs first.

More cubic inches means higher billable weights and more surcharge trips. This guide breaks down what’s changing, who’s hit hardest, and the fastest ways to protect margin.

FedEx & UPS DIM Rounding Rule (Aug 18, 2025): What’s Changing & How to Cut Costs