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An LTL rate API is a connection that lets a TMS, ERP or storefront send shipment details to a rating engine and get less-than-truckload prices and transit times on demand.
LTL is the hardest freight mode to rate by machine. A parcel request needs a weight and two postal codes. An LTL request also needs handling units, dimensions, a freight class or density, and the accessorials the pickup and delivery sites require. Miss one and the price you showed your buyer is not the price on the carrier invoice. LTL rating is one of the request types covered by the ExFreight freight API, and this guide explains what a well-built LTL rate call sends, what it should return, and where the money leaks.
Key takeaways
- An LTL rate API is only as accurate as the handling-unit dimensions and weight you send. Density drives class, and class drives price.
- Accessorials (liftgate, residential, appointment, limited access) must be declared in the request, not discovered at delivery.
- Since NMFTA’s Docket 2025-1 took effect on July 19, 2025, density matters for far more commodities, so dimension capture belongs in your order data, not on the dock.
What an LTL rate API returns
A rate response is a list of options, not a single number. Each option ties a carrier service to a price and a transit estimate for the exact freight described in the request. A complete response gives your system enough to rank, display and later book the option without a second lookup.
- Total charge and its parts. Linehaul after discount, fuel surcharge, and each priced accessorial as a separate line. A single total with no breakdown is hard to audit against the carrier invoice.
- Transit estimate. Business days from pickup, which you convert to an estimated delivery date using your own calendar logic. Treat it as an estimate: LTL transit is not a commitment unless a time-definite service is bought as a chargeable accessorial.
- Carrier and service identifiers. The values your booking call will send back to select this option.
- Quote reference and validity. An ID and an expiry, so the booking can reference the priced option instead of re-rating.
- Volume LTL or truckload alternatives. Larger shipments may price better as volume LTL or a full truckload. Some rating engines return these side by side; the ExFreight platform shows LTL, volume LTL and FTL rates simultaneously based on the freight parameters.
For the pricing mechanics behind those numbers (base rates per hundredweight, discounts, minimum charges and fuel), see how LTL shipping rates work. The API does not change that math. It only automates the inputs and returns the result in a form your software can use.
Request fields: class, density, handling units, accessorials
LTL requests fail quietly. The call succeeds, a rate comes back, and the error only surfaces when the carrier reweighs or measures the freight. These are the fields that decide whether the quoted rate survives contact with the dock.
| Field | Example | Why it matters |
|---|---|---|
| Origin and destination postal code | 30336 to 75261 | Sets the lane, the carrier’s service area and the transit estimate. |
| Location type | Business dock, residential, limited access | Residential and limited-access sites carry accessorial charges and may need a smaller truck. |
| Handling units | 4 pallets | Carriers rate and load by unit. Two pallets stacked as one unit are not the same freight as two units. |
| Dimensions per unit | 48 x 40 x 50 in | Feeds density, cubic capacity and linear-foot checks. |
| Weight per unit (with pallet) | 450 lb | Billed weight. Carriers reweigh at terminals. |
| Freight class or NMFC item | NMFC item and sub, or density | Selects the rate column in the carrier tariff. |
| Stackable flag | No | Non-stackable freight consumes the floor space above it and can trigger cubic or linear-foot charges. |
| Accessorials | Liftgate at delivery, appointment | Each one is a priced line. Undeclared accessorials are billed after delivery. |
| Pickup date | Next business day | Rates and capacity can differ by date; transit is counted from pickup. |
Worked example: density from the order record
Four pallets, each 48 x 40 x 50 inches and 450 lb. Volume per pallet is 48 x 40 x 50 = 96,000 cubic inches, divided by 1,728 = 55.6 cubic feet. Density is 450 / 55.6 = 8.1 pounds per cubic foot (pcf). The shipment is 1,800 lb and 222 cubic feet.
Now assume the warehouse system stored the pallet height as 40 inches, the height before the top tier was added. The API calculates 44.4 cubic feet per pallet and 10.1 pcf. That two-point difference can cross a density break in the classification, which means a lower class and a lower quote than the carrier will bill after it measures the freight. The fix is not in the API. It is capturing measured dimensions as tendered, per handling unit, and sending those. NMFTA’s own guidance for the 2025 changes says the same: start capturing handling unit dimensions and weight as tendered to the carrier.
The density-based pricing guide covers why density-based rating reduces class disputes, and the freight class and NMFC guide covers the classes themselves. For integration, the rule is simpler: send real dimensions and weight per unit, and let the rating engine apply them.
Aggregators, carrier APIs and NMFTA standards
There are three common ways to get LTL rates into software, and many shippers end up using more than one.
| Single-carrier API | Multi-carrier rating platform | Forwarder or broker rating API | |
|---|---|---|---|
| Carriers per call | One | Many, using your carrier contracts | Many, using the provider’s carrier network and pricing |
| Contracts needed | Your account with that carrier | Your accounts with each carrier | An account with the provider |
| Integration work | One build per carrier, each with its own schema | One build to the platform | One build to the provider |
| Who handles billing disputes | You and the carrier | You and each carrier | The provider helps facilitate them with the carrier |
| Best fit | High volume concentrated on one or two carriers | Shippers with negotiated contracts across several carriers | Shippers who want carrier choice without managing carrier contracts |
Multi-carrier platforms often rely on industry rate bases. SMC³ tools such as RateWare XL and CzarLite are long-standing references for LTL base rates and transit, and connectors such as project44 and Banyan pass rate requests to carriers on behalf of TMS users. ExFreight already has integrations with TMS systems including Project 44, Accufrate, Banyan, SAAS, 7L, Primus, Pacejet, CSA Software and Teknowlogi, so some shippers reach ExFreight rates through software they already run.
Schema fragmentation is the main cost of single-carrier builds. NMFTA’s Digital Standards Development Council publishes open LTL and truckload API standards to reduce it, and is developing a Preliminary Freight Charges (PFC) standard to give shippers and 3PLs visibility into charge changes such as reweighs, reclassifications and accessorials as shipments move. When you evaluate any LTL API, ask which of these standards it follows today.
Reclass and accessorial risk
Most of the gap between an LTL quote and an LTL invoice comes from four sources: reweigh, reclassification, undeclared accessorials, and cubic or linear-foot rules for freight that takes more trailer space than its weight suggests.
The 2025 NMFC update raised the stakes on the first two. According to NMFTA’s 2025 NMFC changes overview, Docket 2025-1 introduced a standardized density scale for LTL freight, added lower density classes for heavier freight, and warned that NMFC item, sub and freight class may change for existing products. The changes took effect July 19, 2025. If your product master still holds a class assigned years ago, your API requests may be sending a class the carrier no longer agrees with.
Quotes are informational and subject to change. If the weight, dimensions, class, location type or services found at pickup or delivery differ from the request, the shipment can be re-invoiced to match the actual details. Accurate handling-unit data is the only reliable protection.
ExFreight’s rating uses density-based pricing for LTL, and when it receives accurate weight and dimensions it helps shippers avoid unanticipated additional charges tied to class disputes. Cubic capacity and linear-foot protection functionality on the platform addresses the space-based charges. Neither protects a request built on wrong data.
Accessorials need the same discipline. Map each one to a field your order system already holds: a residential flag from the ship-to address type, liftgate from the consignee profile, appointment from the customer’s receiving rules. If a field is unknown, do not default it to “no”. Default it to the more expensive assumption and let your team downgrade it. For how base rates, minimum charges, fuel and accessorials add up on the final bill, see the LTL shipping costs guide.
Putting the rate call to work
Teams that get LTL rating right treat the API call as the end of a data process, not the start. A practical sequence:
- Fix the product master. Store per-SKU pallet patterns, measured dimensions, weight with packaging, and the current NMFC item. Review classes against the 2025 changes.
- Build units, not orders. Convert order lines into handling units before rating. Rate what will actually be tendered. The e-commerce freight API guide walks through a pallet build from carton data.
- Derive accessorials from addresses. Classify consignees once (dock, residential, limited access) and reuse the flag.
- Store the quote ID. Book against the priced option so the booking references what was quoted. The freight quote API guide covers request and response handling across modes.
- Close the loop. Compare invoiced weight, class and accessorials to the request each week. Each recurring variance points to a field to fix upstream.
Shippers who prefer to start with a manual workflow can rate on the platform first and automate later. The ExFreight LTL freight service is where trucking shipments are quoted and booked; for trucking-only shipments ExFreight acts as a freight broker (FMCSA MC-677423-B), not the carrier.
What ExFreight’s API covers today
The APIs are available upon request, with a test environment and assistance from the ExFreight team. Connectivity gives access to ExFreight’s online rating, booking and tracking system. See how the ExFreight freight API works
Freight API series
Frequently asked questions
How to calculate LTL freight rate?
Carriers start from a base rate per hundredweight for the lane and freight class, apply your discount and any minimum charge, then add a fuel surcharge and priced accessorials such as liftgate or residential delivery. Class increasingly depends on density, so accurate dimensions and weight per handling unit drive the result.
What does LTL rate mean?
An LTL rate is the price to move a less-than-truckload shipment, freight that shares a trailer with other shippers. It reflects the lane, weight, freight class or density, minimum charge, fuel surcharge and accessorial services. It is normally quoted per shipment and can change if the tendered freight differs from the details quoted.
What is API in trucking?
In trucking, an API (application programming interface) is a connection that lets a shipper, broker or TMS exchange data with carrier or provider systems on demand. Typical trucking API calls request LTL or truckload rates, book or tender a load, retrieve status updates and pull documents or invoices without manual portal work.
Does an LTL rate API price by the mile?
No. An LTL rate API prices by lane, density or freight class, and accessorials, using per-hundredweight base rates, minimum charges and fuel surcharges. Cost per mile varies too widely between shipments on the same lane to plan with. Rate the actual shipment with its real dimensions, weight and services, then compare the returned options.
