In 1781, the story goes, James Watt needed to convince skeptics to ditch their draft horses and buy his new steam engine. To prove his machine’s superiority, he measured a horse walking in circles to turn a grindstone in a mill. He multiplied the distance it walked by its roughly 180 pounds of pulling force, divided by the time it took, and came up with a new measure: horsepower. (His new engine did the work of 35 nags, about the same as today’s riding mower.) We still use his math to sell F-150s, but it can feel kind of abstract. So we came up with a few new ways to visualize one horsepower.