CAT Scale Weighing Calculator: Compute True Tongue Weight, Pin Weight, FALR & Axle Margins
Interactive commercial weighbridge ticket solver: enter your Steer, Drive, and Trailer axle weights from 3 passes (bumper-pull with WDH) or 2 passes (fifth wheel / dead-weight hitch) to compute true raw coupling weight, WDH Front Axle Load Restoration (FALR %), and pass/fail margins against Front GAWR, Rear GAWR, GVWR, Trailer GVWR, and GCWR. Paired below with a 2024 Ford F-150 Lariat 3.5L EcoBoost benchmark towing a 7,600 lb camper (988 lbs raw / 899 lbs net tongue, +301 lb payload reserve).
Interactive 3-Pass & 2-Pass CAT Scale Ticket Solver
Enter your commercial weighbridge Steer, Drive, and Trailer pad weights to compute true coupling load, WDH FALR %, and 5-rating margins.
3-Pass & 2-Pass CAT Scale Mass-Balance Formulas
Every weighbridge figure above solves directly from Newton’s static vertical equilibrium across Platform 1 (Steer), Platform 2 (Drive), and Platform 3 (Trailer). Need the truck-stop lane procedure first? See our step-by-step 3-pass CAT Scale weighbridge field guide .
Net Truck Coupling (WDH Active) = (Steer1 + Drive1) − (Steer3 + Drive3)
Loaded Trailer Gross (GVW) = (Steer1 + Drive1 + Trailer1) − (Steer3 + Drive3)
SAE J2807 FALR % = [(Steer1 − Steer2) / (Steer3 − Steer2)] × 100
Coupling load (988 lb raw / 899 lb net) counts against door payload.
2024 Ford F-150 Lariat 4WD SuperCrew Grade & Altitude Summary
SAE J2807 6% Davis Dam thermal climb and 10,000 ft elevation output for 3.5L EcoBoost Twin-Turbo V6 (400 hp / 500 lb-ft):
MATRIX F-150 Trailer Sensitivity (-20% to +20% Around 7,600 lbs)
2024 Ford F-150 Lariat 4WD SuperCrew Trailer Weight Sensitivity (3.55 Axle)
Five loaded weight steps around 3-Pass Audited Tandem Travel Trailer (6,200 lb dry UVW) with 340 lb cabin and 95 lb cargo fixed:
| Simulation Tier | Loaded Trailer | 13% Tongue (Net) | Total Payload Used | Remaining Margin | Combined GCW | SAE J2807 Verdict |
|---|---|---|---|---|---|---|
| Light Camp Load (-20%) | 6,100 lbs | 793 lbs (722 net) | 1,242 / 1,720 lbs | +478 lbs (72%) | 12,000 / 17,100 lbs | OPTIMAL |
| Reduced Gear Load (-10%) | 6,850 lbs | 891 lbs (811 net) | 1,331 / 1,720 lbs | +389 lbs (77%) | 12,750 / 17,100 lbs | OPTIMAL |
| Nominal Target Rig (0% (Base)) | 7,600 lbs | 988 lbs (899 net) | 1,419 / 1,720 lbs | +301 lbs (83%) | 13,500 / 17,100 lbs | OPTIMAL |
| Full Water & Gear (+10%) | 8,350 lbs | 1,086 lbs (988 net) | 1,508 / 1,720 lbs | +212 lbs (88%) | 14,250 / 17,100 lbs | NEAR LIMIT |
| Heavy Stress Test (+20%) | 9,100 lbs | 1,183 lbs (1,077 net) | 1,597 / 1,720 lbs | +123 lbs (93%) | 15,000 / 17,100 lbs | NEAR LIMIT |
Exact Mass-Balance Equations: Tongue Weight, WDH Front Axle Load Restoration (FALR %) & True Trailer GVWR
Commercial 3-platform truck scales measure vertical tire reactions to the nearest 20 lbs. In a 3-pass Weight Distribution Hitch audit (Pass 1 hitched with WDH tensioned, Pass 2 hitched with WDH spring bars unhooked and stored in the bed, Pass 3 truck solo unhitched), True Raw Tongue Weight equals (Steer_2 + Drive_2) minus (Steer_3 + Drive_3), while Net Coupling Load carried by the truck with WDH active equals (Steer_1 + Drive_1) minus (Steer_3 + Drive_3). By conservation of mass, True Loaded Trailer Weight equals Combined Gross Weight (Steer_1 + Drive_1 + Trailer_1) minus Solo Truck Weight (Steer_3 + Drive_3).
To verify steering stability under SAE J2807 Section 4.4.2, compute Front Axle Load Restoration: FALR % = ((Steer_1 minus Steer_2) / (Steer_3 minus Steer_2)) x 100. Restoring 50% to 100% of the front steer weight lost on Pass 2 prevents highway understeer without over-loading the trailer A-frame above Steer_3.
Pass/Fail Audit Against Your Door-Jamb Sticker: Front GAWR, Rear GAWR, Truck GVWR, Trailer GVWR & GCWR
Every road-ready rig (Pass 1) must satisfy five simultaneous inequalities against your driver B-pillar certification label and trailer VIN tag: (1) Steer_1 <= Front GAWR, (2) Drive_1 <= Rear GAWR (3,704 / 4,150 lbs on our F-150 Lariat benchmark for a +446 lb margin), (3) Steer_1 + Drive_1 <= Truck GVWR (6,799 / 7,100 lbs, +301 lb reserve), (4) True Loaded Trailer Weight <= Trailer GVWR, and (5) Combined Gross Weight <= SAE GCWR (13,500 lbs combined GCW vs 17,100 lb GCWR).
Where to Stop Your Tires on the 3 CAT Scale Platforms (Steer, Drive, Trailer Pads)
Pull onto the scale so front truck tires rest on Pad 1 (Steer), rear truck tires rest on Pad 2 (Drive, forward of the yellow concrete divider), and all camper axles rest on Pad 3 (Trailer). Need the full staging-lot unhitching sequence and Weigh My Truck app walkthrough? Read our companion field station guide on how to weigh your truck and trailer at a CAT Scale.
Frequently Asked Questions (2024 Ford F-150 Towing)
FAQ How do you calculate trailer tongue weight from two or three CAT Scale weigh slips?
Subtract your unhitched Solo Truck Gross Weight (Pass 3: Steer + Drive) from your Hitched Truck Gross Weight without WDH tension (Pass 2: Steer + Drive). In a 2-pass fifth-wheel or dead-weight weigh-in without WDH, simply subtract Pass 2 Solo Truck GVW from Pass 1 Hitched Truck GVW.
FAQ Do you need 2 or 3 passes at a CAT Scale for a fifth wheel vs a travel trailer with WDH?
Only 2 passes are needed for a fifth wheel, gooseneck, or dead-weight utility/boat trailer without WDH spring bars (Pass 1 hitched, Pass 2 solo truck). All 3 passes are required whenever you run a Weight Distribution Hitch so you can isolate raw ball weight on Pass 2 and compute FALR % on Pass 1.
FAQ How much does a CAT Scale weigh and reweigh cost via the Weigh My Truck app?
As of 2026, an initial CAT Scale weigh costs roughly $13.50 to $14.00, and unlimited same-day reweighs referencing your original ticket number cost roughly $4.00 each ($21.50–$22.00 total for a complete 3-pass RV calibration) with instant PDF tickets in the Weigh My Truck app.
Related SAE J2807 Specs Audits & Calculators
Browse SAE J2807 Towing Standard, GCWR & Davis Dam Grade Specs matchups alongside Ford F-150: