Two hazards worth naming before any arithmetic
Rollover and PTO entanglement are the two things that kill people around tractors, and neither announces itself. A tractor can roll before the operator feels it beginning — a raised load moves the centre of gravity up and forward, a slope or a turn does the rest, and the point of no return arrives without a warning stage. What makes a rollover survivable is a rollover protective structure and a seatbelt worn together; the structure alone does not help someone who has been thrown out of the seat, and the belt alone does not help without the structure. A rotating PTO shaft catches clothing faster than a person can react to it, and a shaft that is turning is dangerous whether or not it is doing work.
That is a statement of what the hazards are. It is not a procedure, and this page will not offer one. Operating instruction comes from the manual for your specific machine, from the manufacturer, and from proper training.
The moment balance, in full
Take moments about the front axle. That is the pivot the arithmetic cares about, because it is the line the machine would rotate about if the rear wheels lifted.
A load of weight P sitting a distance d ahead of the front axle applies a moment of P times d, trying to rotate the tractor nose-down. The only thing resisting that moment is the weight on the rear axle acting at the end of the wheelbase, a lever of length L. So the rear axle load changes by P times d divided by L — that quantity leaves the rear and, together with the load itself, arrives at the front.
Worked through: a tractor with 3,000 lb on the front and 5,000 lb on the rear, wheelbase 90 inches, lifting 2,500 lb whose centre sits 45 inches ahead of the front axle. The transfer is 2,500 times 45 divided by 90, which is 1,250 lb. The rear drops to 3,750 lb and the front rises to 3,000 plus 2,500 plus 1,250, which is 6,750 lb. The two axles sum to 10,500 lb, which is the 8,000 lb tractor plus the 2,500 lb load, so nothing has gone missing.
Set the rear reaction to zero and you can solve for the load that gets you there: P equals rear weight times wheelbase divided by d, which in this case is 5,000 times 90 over 45, or 10,000 lb. That figure is a property of the arithmetic. It is emphatically not a limit, a rating, or a threshold to work near — a real machine stops behaving predictably long before a model runs out of rear axle reaction, and it does so on ground that is never as flat as an equation assumes.
Why distance does more than weight
Both P and d multiply, so a pound further out costs the same as more pounds closer in. That is why the reach table on the results matters more than it looks. The distance to use is not the distance with the bucket tucked back at carry height; it is the worst case the load will see — raised, extended, and dumped forward, which is exactly the moment a bucket is being emptied over the side of a trailer.
| Change | Effect on the transfer | Why |
|---|---|---|
| Twice the load, same reach | Doubles | Linear in P |
| Same load, twice the reach | Doubles | Linear in d, exactly as much |
| Longer wheelbase | Reduces | L is in the denominator |
| Raising the load | Increases | The arc carries the load forward as it rises on most loaders |
The last row is the one operators discover by feel. On most loader geometries the load moves forward as it rises through the middle of its travel, so the transfer is not constant through a lift; it grows and then changes again near full height.
What ballast actually does
Rear ballast works on the same lever, from the other side. A weight B sitting a distance b behind the rear axle adds B times the quantity (L plus b) over L to the rear axle, and takes B times b over L off the front. Those two figures sum to exactly B, which is the arithmetic check that the model is consistent — all the weight you hung on has to land somewhere.
Because the rear gain scales with (L plus b), ballast hung further back does more per pound. A thousand pounds 30 inches behind a 90 inch wheelbase adds 1,333 lb to the rear axle and takes 333 lb off the front. The same thousand pounds bolted right at the axle would add only the thousand. That is why ballast boxes hang out on the three-point rather than sitting on the drawbar, and it is also why a mounted implement makes an indifferent counterweight when it is carried tight to the machine.
Note what ballast does not do: it does not reduce the total weight on the ground, and it does not reduce the load on the front axle caused by the lifted load — it only offsets part of it. Every pound of ballast is a pound the tyres, the axles and the ground have to carry, and the front axle is still carrying the load plus the transfer minus a fraction of the ballast.
Why this page issues no verdict
A weight distribution is a number. Stability is not. Whether a given arrangement behaves acceptably depends on the tyres and their pressures, the track width, the ground surface and its slope, the speed, whether the load is loose or fixed, how it moves in the bucket, whether the front axle can oscillate, what the loader and tractor are rated for, and what the operator manual says. None of that is on this page and none of it can be inferred from four numbers.
So the calculator reports the transfer, the resulting axle loads, and the ballast that would return the rear axle to a figure you nominate. It does not say the result is fine, and it will not say so however the numbers come out. The manufacturer of the tractor and the manufacturer of the loader set the limits; the manual is where they are written down. If you want the same style of moment arithmetic for a load on a trailer instead, the tongue weight calculator takes moments about the trailer axle, and the towing and payload calculator checks the result against the ratings stamped on the vehicle.
Questions people ask
Where do I get the front and rear axle weights?
A scale. Drive the front axle onto a platform scale and read it, then the rear, with the loader mounted and empty and the machine in the configuration you actually work in. Brochure weights describe a base machine without fluid in the tyres, without wheel weights, and often without the loader, and every one of those absences is worth hundreds of pounds. A public truck scale that will let you take an axle at a time works, and so does a farm scale. Guessing the split defeats the whole calculation, because the transfer is compared against the rear figure.
Is there a rear weight percentage I should aim for?
This page will not name one, and you should be wary of any that gets quoted without reference to a specific machine. Guidance on ballasting exists, and where it exists it comes from the tractor manufacturer for that model with that loader, in the operator manual and the loader documentation. Those figures account for the axle ratings, the steering, the brakes and the intended use, none of which a general calculator knows. The target field here exists so you can test an arrangement against a figure you have obtained from the manual, not so the page can supply one.
Does fluid in the tyres count as ballast?
It counts as weight on the rear axle, and in this calculator it belongs in the rear axle weight rather than the ballast box. Fluid fill and wheel weights act at the axle, so their lever arm behind the axle is effectively zero and they add their weight and nothing more. The ballast field is for weight hung behind the axle — a ballast box, weights on the three-point, a mounted implement — where the extra lever arm makes each pound do more than a pound. Weighing the machine as it stands captures the fluid automatically, which is another reason to weigh rather than calculate.
What distance should I enter for the load centre?
The worst case, not the comfortable one. Measure horizontally from the front axle centreline forward to where the centre of gravity of the load sits, with the loader in the position that puts it furthest forward. On most loaders that is not the carry position: the load tracks forward as the arms rise, and dumping rolls it further forward again. If you are unsure, use the larger distance, because the model is linear in that number and being optimistic about it is being optimistic about everything downstream.
Does this model handle slopes?
No, and that is the largest thing it leaves out. It is a static, level, two-dimensional balance of vertical forces about two axles. A slope changes the direction of gravity relative to the machine and introduces a sideways component that this arithmetic has no term for, which is exactly the situation in which real machines get into trouble. Braking, acceleration, a swinging load and an oscillating front axle are also absent. Treat the output as an indication of how much weight redistribution a load causes on flat ground, and nothing broader.