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Status: {{ statusLabel }} Weakest limit: {{ weakestLimitLabel }} Loaded: {{ loadedWeightDisplay }}
A profile is a starting point, not a manufacturer rating.
Use the top-line loaded-trailer limit from the label.
Enter the starting weight before the additional loads below.
Use zero when the scale weight already includes these items.
This load consumes payload before loose cargo is added.
This is the cargo load whose remaining margin is reported.
From 0% to 25% of GVWR.
%
This estimate affects axle and tire load, not tow-vehicle capacity.
%
Enter the rating for the full trailer axle group.
Do not enter a single-tire rating unless the trailer has only one tire carrying the axle load.
The neutral default is 0 lb. This changes the warning threshold, not the legal ratings.
Capacity breakdown
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Weakest-limit method:
Every row uses the same canonical result as the summary, chart, and rating checks.
margin = min(reserve GVWR, axle equivalent, tire equivalent) − loaded weight
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Usable limits against {{ loadedWeightDisplay }} loaded

Teal bars show each usable limit; the blue line marks the loaded estimate.

The chart renderer is unavailable. The same limits remain available in the breakdown and checks.

CheckStatusMargin or loadNext actionCopy
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Trailer Tongue Weight Calculator Calculate trailer tongue weight from direct or lever readings and vehicle-scale tickets with checks for balance, hitch capacity and payload.
Tie Down Strap Capacity Calculator Plan cargo tie-down count and capacity from weight, WLL, strap path, blocking, and length rules with weak-link and margin checks.
Car Tire Pressure Calculator Plan front and rear cold tire pressure from placard values and trip load with axle-share, temperature-change and equipment-limit checks.
Tire Size Comparison Calculator Compare tire sizes for diameter, width, ride-height and speedometer changes with fitment screening and measured-clearance checks.

Trailer payload is the weight added to the trailer above its empty or measured starting weight. Cargo is only part of it. Batteries, racks, spare tires, propane, water, fuel, tools, and permanent modifications can consume capacity before the first loose item is loaded.

The gross vehicle weight rating (GVWR) limits the fully loaded trailer, while the gross axle weight rating and tire capacities limit the portion carried by the trailer wheels. Some loaded weight is carried at the coupler as tongue weight, so axle and tire loads are not normally equal to the trailer's full scale weight.

  • GVWR comes from the trailer certification label and governs total loaded trailer weight.
  • Axle group rating is the combined rating for the trailer axle group, not one axle end or one tire.
  • Combined tire capacity is the sum of the applicable trailer-tire ratings at the pressure and conditions used.
  • Payload reserve is a planning cushion below GVWR, not a replacement or increase for any legal rating.

The usable cargo amount is controlled by the weakest relevant limit. A trailer can remain below GVWR while exceeding an axle or tire capacity after weight distribution is considered. Conversely, high axle and tire ratings do not permit the trailer to exceed its GVWR.

An estimated tongue share helps split loaded trailer weight between the coupler and trailer axle group. It does not check the tow vehicle's payload, rear axle, tires, receiver, hitch hardware, or gross combined weight rating. Those limits require a separate tow-vehicle calculation and, preferably, scale measurements.

A safe plan uses current label ratings and road-ready scale weights. Brochure dry weight and generic trailer profiles are starting estimates; they often exclude options, fluids, accessories, and cargo. Load security and distribution still matter after every number clears.

How to Use This Tool:

Use a profile to explore, then replace every rating and weight with values from the actual trailer and trip.

  1. Enter Trailer GVWR from the certification label and the trailer's Empty or scale weight. The starting weight must be strictly below GVWR.
  2. Add fixed equipment and carried fluids only when they are not already included in the scale weight. Enter the planned loose cargo separately.
  3. Choose a payload reserve from 0% through 25%. This lowers the planning limit below GVWR without changing the manufacturer's rating.
  4. Enter the estimated tongue share and the full Axle group rating. Add the combined capacity of all trailer tires carrying the axle load, not a single-tire value.
  5. Use Extra cushion target only when the desired warning margin exceeds the built-in 150 lb or 3% of GVWR check.
  6. Review the weakest limit, usable cargo capacity, cargo margin, and every rating check. Remove or redistribute load and re-weigh whenever a margin is negative or unexpectedly small.

Interpreting Results:

Usable cargo capacity is the loose-cargo allowance remaining after empty weight, fixed add-ons, fluids, reserve, axle rating, tire capacity, and estimated tongue share are reconciled. Cargo margin subtracts planned loose cargo from that capacity.

Over limit means at least one controlling margin is strictly negative. A zero margin is not over, but it remains tight because no usable cushion is left. Tight margin applies when cargo margin is below the larger of 150 lb, 3% of GVWR, or the entered extra cushion. Equality at that threshold counts as Capacity clears.

The weakest-limit label identifies the current mathematical constraint among reserve-adjusted GVWR, the axle group, and trailer tires. It does not certify the whole towing combination. Compare the estimated tongue load with tow-vehicle payload, receiver, hitch, and rear-axle limits separately.

Technical Details:

Masses are normalized to kilograms using exactly 1 lb = 0.45359237 kg. Display-unit changes preserve the physical mass. The model treats entered fixed add-ons, fluids, and loose cargo as additions to the entered empty or scale weight.

Formula Core

Let G be GVWR, E empty or scale weight, F fixed add-ons, U fluids, C planned loose cargo, and r the reserve percentage.

loaded weight=E+F+U+C raw payload capacity=G−E reserve loaded limit=G×(1−r100)

Tongue share t% leaves an axle share q = 1 − t/100. Dividing the entered axle and combined-tire ratings by q translates them into equivalent whole-trailer loaded limits.

tongue load=loaded weight×t100 axle load=loaded weight×q axle-equivalent limit=axle group ratingq tire-equivalent limit=combined tire capacityq

The controlling loaded limit is the smallest of the three comparable limits. The remaining cargo result removes starting weight and non-cargo loads from it.

Leffective=min(reserve GVWR limit,axle-equivalent limit,tire-equivalent limit) usable cargo capacity=Leffective−E−F−U cargo margin=usable cargo capacity−C

Rule Core

RuleExact behavior
Starting-weight validityEmpty or scale weight must be strictly less than GVWR
Reserve and tongue domainsReserve is 0% to 25%; tongue share is 1% to 35%, both inclusive
Over statusCargo, raw GVWR, axle, or tire margin < 0
Tight thresholdMaximum of 68.0388555 kg (150 lb), 3% of GVWR, and entered extra cushion
Clear statusNo negative rating margin and cargo margin ≥ the tight threshold

Worked Examples:

Travel trailer with a reserve

A trailer rated at 7,600 lb starts at 6,100 lb, then carries 180 lb of fixed add-ons, 360 lb of fluids, and 520 lb of loose cargo. With a 5% reserve and 12.5% tongue share, the reserve-adjusted GVWR is the weakest limit. Usable loose-cargo capacity is about 580 lb, leaving roughly 60 lb of cargo margin. That is below the built-in 228 lb threshold of 3% of GVWR, so the result is Tight margin even though the raw GVWR margin is 440 lb.

Safety and Accuracy Notes:

Use certified label ratings and weigh the loaded trailer by axle on a suitable scale. Do not increase a rating because another component has spare capacity; the lowest applicable manufacturer limit controls.

  • Check the tow vehicle's payload, front and rear axle ratings, tires, receiver, hitch hardware, and gross combined rating separately.
  • Confirm cold tire pressures and the capacity of every trailer tire, then add only the tires that actually carry the axle load.
  • Secure cargo against movement and re-weigh after changing cargo, fluids, accessories, hitch setup, or weight distribution.
  • Stop and obtain qualified help when labels are missing, scale readings conflict, tires are mismatched, or the trailer sways.

References: