Horsepower to Foot-pounds per Second for Winch Pulls

Working Out What a Winch Really Does at the Drum

A winch spec sheet gives you two numbers that never appear together: a rated line pull in pounds and a line speed in feet per minute, each measured at a different load. Multiply a pull by a speed and you get foot-pounds per second — the actual rate of work at the drum — and suddenly the whole spec makes sense, because that figure barely moves while pull and speed trade against each other all the way up the load range.

Conversion factor: 1 hp = 550 ft·lb/s exactly. Line speed is quoted per minute, so divide by 60 first: a winch holding 8 000 lb while the rope comes in at 4.5 ft/min is 8 000 × 4.5 ÷ 60 = 600 ft·lb/s, which is 1.09 hp at the drum.

Reading the Two Halves of a Winch Rating

Rated pull is a bare-drum number

The headline figure on the box is measured on the first wrap of rope, with the drum as small as it will ever be. Every layer wound on top of it costs pull, so the rating is the best case rather than the working case.

Line speed only means something with a load beside it

Manufacturers publish a table of speeds at 0, 2 000, 4 000 lb and so on. A single quoted speed with no load attached is almost always the free-spooling figure and tells you nothing about a recovery.

Rigging changes both halves at once

Run the rope through a snatch block and the load sees roughly double the pull at half the speed. The work rate at the drum is unchanged — the winch is doing the same job, only geared differently by the rigging.

Drum power is not motor power

Around a horsepower leaves the drum while the motor is drawing several kilowatts from the battery. The difference is heat in the windings and the gear train, and it is why pulls have to be kept short.

Checking a Winch Spec Before You Rig the Pull

Whether you are choosing a winch or working out how long a recovery will take, the arithmetic is the same: pull times speed, divided by sixty, then into horsepower.

Work out the foot-pounds per second first

Take a matching pair from the manufacturer's load-and-speed table — say 12 000 lb at 3.4 ft/min — and multiply, then divide by 60. That gives 680 ft·lb/s, the honest work rate for that point on the curve.

Enter it and swap to see it in horsepower

This page starts on hp → ft·lb/s, which is the direction for turning a motor rating into a work rate. Press the swap button (↔) to run ft·lb/s → hp and drop your 680 straight in; 1.24 hp comes back.

Try the other points on the same curve

Both fields stay live, so you can walk the whole table — full load, half load, free spool — and watch how little the horsepower changes even as line speed quadruples. That is the trade-off in plain numbers.

Carry the bare figure over to the electrical side

Copy hands over the plain number with no unit attached, ready to sit next to the current draw in a build sheet. Switch a dropdown to watts and the same result lines up with battery and cable ratings.

Match the pull to the speed: multiplying a rated pull by a free-spool speed produces a horsepower figure several times higher than any winch on the market can deliver. Always take the two numbers from the same row of the manufacturer's table.

Winch Classes, Line Pull and Drum Power

Representative recovery winches with a load and the line speed that goes with it, converted to the work rate at the drum and then to horsepower. The last electric row deliberately repeats an earlier winch at a lighter load.

Winch class	Load × line speed	Work rate at the drum	Horsepower
ATV and side-by-side, 3 500 lb	3 500 lb × 7 ft/min	408 ft·lb/s	0.74 hp
Light truck winch, 8 000 lb	8 000 lb × 4.5 ft/min	600 ft·lb/s	1.09 hp
Mid-size 4x4 winch, 9 500 lb	9 500 lb × 4 ft/min	633 ft·lb/s	1.15 hp
Heavy 4x4 winch, 12 000 lb	12 000 lb × 3.4 ft/min	680 ft·lb/s	1.24 hp
Full-size competition winch, 16 500 lb	16 500 lb × 2.6 ft/min	715 ft·lb/s	1.30 hp
The same 12 000 lb winch, part loaded	3 000 lb × 14 ft/min	700 ft·lb/s	1.27 hp
Hydraulic PTO winch, 20 000 lb	20 000 lb × 8 ft/min	2 667 ft·lb/s	4.85 hp
Wrecker planetary winch, 30 000 lb	30 000 lb × 6 ft/min	3 000 ft·lb/s	5.45 hp

The sixth row is the one worth staring at. A 12 000 lb winch pulling a quarter of its rating runs four times faster, and the work rate barely shifts — 700 ft·lb/s against 680. That is the pull-versus-speed trade in a single comparison: the motor makes roughly the power it makes, and the gearing decides how it is spent. It also explains why the whole electric column sits near one horsepower while a hydraulic winch driven off an engine PTO is in another league entirely.

What Helps When You Are Comparing Winches

Both boxes live while you try pull-and-speed pairs

Type in either field and the other follows, so a full manufacturer's load table can be worked through in one go without resetting anything between rows.

Flip when the work rate is what you already have

Most winch arithmetic produces foot-pounds per second and wants horsepower back, which is one press of the swap arrows away.

Watts on the dropdown for the electrical side

The searchable unit lists include W and kW, so the drum figure can be set beside the volts and amps the motor is pulling out of the battery.

Bare figures for the build sheet

Results run to eight decimals with thousands spaced apart for reading, while copy returns the plain number a spreadsheet or forum post needs.

Winching and Recovery Questions

Why does the rope slow to a crawl as the load comes on?

Because the motor can only make so much power, and pull times speed is that power. A series-wound winch motor produces its torque by slowing down under load: free spooling it might run 30 ft/min, at half rating perhaps 8, at full rating 3 or less. The product of the two hardly changes across that range. If the rope has stopped moving altogether you are at stall, where all the power is going into heat and none into the recovery.

Does the rating still apply once the drum is half full of rope?

No, and this catches people out constantly. Rated pull is measured on the first layer, where the effective drum radius is smallest. Each layer wound on top increases the radius, so the same drum torque produces less pull and more speed — by the fourth or fifth layer a 12 000 lb winch may be down near 7 000 lb. Spool most of the rope out before a heavy pull, or run it through a snatch block back to the vehicle so the working wraps stay low on the drum.

If a snatch block doubles my pull, where does the extra come from?

From time. The block is a two-to-one purchase: the vehicle moves half as far for every foot the drum takes in, so it moves at half the speed while feeling roughly twice the pull. The drum is doing the same work per second either way — nothing is created. Real blocks lose a few per cent to sheave friction, so call it a little under double, and remember the rigging point and shackle now carry the full doubled load.

How long can I keep pulling before something cooks?

Electric recovery winches are intermittent-duty tools, not machines meant to run continuously. Under a heavy pull the motor is dumping most of its input as heat, so the usual advice is pulls of a minute or two followed by a rest with the engine running to recover the battery. Winding in a smooth surface at light load is far gentler than a long, near-stall drag. A hydraulic winch off the engine can pull all day because the oil carries the heat away.

Why does a 12 V winch pull hundreds of amps if the drum only makes about a horsepower?

Two reasons stacked on top of each other. At 12 volts every kilowatt costs more than 80 amps before any losses, so even a modest motor needs enormous current. Then most of that input never reaches the rope: a heavily loaded winch loses a large share in the motor windings and again in a worm or planetary gear set, so around 5 kW going in can leave barely one horsepower coming out at the drum. That is why heavy cable, clean terminals and a healthy battery matter more to winch performance than almost anything else on the bumper.

Horsepower to Foot-pounds per Second