QUICK EXAMPLE
A 200 hp MFWA tractor (about 170 PTO hp) working at 5 mph should weigh about 19,550 lb, which is 115 lb per PTO hp. With the 40/60 split for front-wheel assist, that is 7,820 lb on the front and 11,730 lb on the rear. If the scales read 7,600 lb front and 10,400 lb rear, the calculator says to add about 220 lb up front and 1,330 lb at the rear.
1Tractor and working speed
MFWA at 5 mphTarget split: 40% front and 60% rear.
Worked out as 85% of engine power.
The speed you actually pull the implement at. Reference range: 4 to 6 mph.
2Axles and tires
Front singles, rear singles3Scale weights
Tractor without implementsWeigh the tractor unhitched, with the fuel and ballast it normally carries. Each entry keeps its value if you switch between axle totals and tire positions.
4Tire fluid option
75% fill, rear tiresTarget tractor weight
19,550 lb
Weight per PTO power
115 lb/hp
Current weight
18,000 lb
Change needed
+1,550 lb
| Axle | Current | Target | Change |
|---|---|---|---|
| Front | 7,600 lb | 7,820 lb | +220 lb |
| Rear | 10,400 lb | 11,730 lb | +1,330 lb |
| Total | 18,000 lb | 19,550 lb | +1,550 lb |
Front axle carries 2.2 points too much: 42% front now, target 40%
What to do
- Add about 220 lb to the front axle with front weights or a suitcase weight carrier.
- Add about 1,330 lb to the rear axle with wheel weights or tire fluid.
- Weigh the tractor again after any change, then check wheel slip in the field.
Tire load and minimum cold pressure
| Axle | Load per tire | Minimum pressure |
|---|---|---|
| Front420/85R28 (16.9R28) | 3,910 lb | 17 psi |
| Rear520/85R38 (20.8R38) | 5,865 lb | 15 psi |
Loads are for 25 mph or slower, cold, singles. Dual tires are rated at 88% of a single. Running a tire below the pressure its load table asks for risks sidewall damage.
Liquid ballast in the rear tires
One tire at 75% fill
142 gal
1,437 lb
Both tires at 75% fill
283 gal
2,874 lb
Fluid can supply all of the 1,330 lb the rear axle needs. That is about 131 gal in total, or 66 gal per tire (46% of a full 75% fill).
With duals, only the inner tires are filled, so the figures above stay at two tires. Gauge a fluid-filled tire with the valve at the bottom, or expect the reading at the top to run about 2 psi low.
Targets cover the tractor alone. Mounted implements and heavy drawbar loads shift weight between axles, and the total must stay under the limit on the tractor's ROPS tag.
AI Insight
Powered by AIGet a plain-English explanation of your results — what they mean for your vehicle and driving experience.
How to Use This Calculator
- Pick the drive type, then enter engine power, PTO power or both. Give one and the other is estimated at 85%.
- Enter the speed you actually pull at. Slower work needs more weight for the same power.
- Choose singles or duals for each axle and select your tire sizes. If your tire is not listed, the tractor tire size calculator helps you compare sizes and diameters.
- Weigh the tractor without implements, then enter one total per axle or one weight per tire position.
- Read the add or remove amounts, the minimum cold pressure and the fluid estimate. For a pressure in another unit, use the PSI to kPa converter.
- Weigh again after any change and check wheel slip. If you also change tire size, the rolling radius calculator shows how it affects wheel speed.
For background on how farm tires are built and rated, read our tractor tire guide and the wider agricultural tire guide.
Recommended Tractor Weight and Axle Split
Total weight is set by power and speed. These are the figures the calculator uses, shown for a 150 PTO hp tractor as an example.
| Working speed | 2WD (lb per PTO hp) | MFWA and 4WD (lb per PTO hp) | 150 PTO hp, 2WD | 150 PTO hp, MFWA or 4WD |
|---|---|---|---|---|
| 4 mph (6.4 km/h) | 160 | 140 | 24,000 lb | 21,000 lb |
| 5 mph (8.0 km/h) | 135 | 115 | 20,250 lb | 17,250 lb |
| 6 mph (9.7 km/h) | 110 | 95 | 16,500 lb | 14,250 lb |
| Drive type | Front | Rear | Range seen in maker guidance |
|---|---|---|---|
| Two-wheel drive | 30% | 70% | 25% to 35% front |
| Front-wheel assist | 40% | 60% | 35% to 40% front |
| Four-wheel drive | 55% | 45% | 50% to 55% front pulling towed tools, 55% to 60% with mounted tools |
Weights per horsepower come from Kansas State University extension publication MF-588. The speed table ends at 6 mph, so the calculator holds the 6 mph figure above that and warns you. Axle splits follow Clemson and Michelin ballast guidance and Titan International's published ranges.
Tire Fluid Ballast Compared
Fluid goes in the rear tires, filled to the valve when it sits at the top (about 75%). The weight per gallon below is for the fluid in the tire.
| Fluid | Weight per gallon | Freeze protection | Worth knowing |
|---|---|---|---|
| Water | 8.3 lb | Freezes solid at 32°F (0°C) | Only for tires that stay above freezing. |
| Calcium chloride, 3.5 lb per gal of water | About 10.1 lb | Slush-free to -12°F (-24°C), solid at -52°F (-47°C) | Can corrode the rim if the solution does not cover it. |
| Calcium chloride, 5 lb per gal of water | About 10.8 lb | Slush-free to -53°F (-47°C), solid at -62°F (-52°C) | Same rim concern. Heavier for the same volume. |
| Beet-juice based ballast | About 9.7 lb | Varies by product | Read the label for weight and freeze rating, since brands differ. |
Water and calcium chloride figures come from the Firestone Ag Data Book 2025 fill tables. The beet-based figure comes from a bio-ballast tire fill table. Calcium chloride numbers assume the type with 77% purity.
How to Check Wheel Slip in the Field
Scale weights get you close. Slip tells you whether the ballast is right for your soil and implement. Drive the tractor under load in your normal gear and count 20 turns of a drive tire, marking where you start and stop with two stakes. Raise the implement, drive the same distance in the same gear and count how many turns it takes. Fewer turns than 20 means the tires were slipping under load.
| Unloaded turns for the same distance | Slip | What to do |
|---|---|---|
| 20 | 0% | Remove ballast |
| 19 | 5% | Remove ballast |
| 18 | 10% | No change |
| 17 | 15% | No change |
| 16 or fewer | 20% or more | Add ballast |
Slip table from Kansas State University extension publication MF-588. Most tires work best between 8% and 15% slip, and about 12% is a sensible target. Before adding weight, check that the tires are not already at their load limit and that the tractor stays under its ROPS weight limit. Our tire load index calculator explains how load index numbers translate to pounds.