- How many inch-pounds are in a foot-pound?
- Exactly 12. A pound of force applied one foot from the pivot is the same twisting effort as a pound of force applied twelve inches from it, because a foot is twelve inches — the force never changes, only the unit the distance is written in. So to go from inch-pounds to foot-pounds, divide by 12; to go back, multiply by 12. There's no rounding involved anywhere in that, which is why this conversion is exact in a way most unit conversions aren't.
- How many foot-pounds is 100 inch-pounds?
- 8.3333 ft-lb — 100 divided by 12, which doesn't come out even. Most torque wrenches don't resolve finer than a quarter foot-pound anyway, so in practice you'd set 8.25 or 8.5 and check whether the spec has a tolerance range. Some other common ones: 45 in-lb is 3.75 ft-lb, 89 in-lb is 7.4167, 120 in-lb is exactly 10, and 600 in-lb is exactly 50.
- Why divide by 12 and not 16?
- Because the 12 comes from inches per foot, not from ounces per pound. This trips people up because both numbers live in the imperial system and both involve the word "pound." But in a torque unit the pound is the force and the inch or foot is the lever arm, so the only conversion happening is a length conversion. Sixteen would be right if you were converting ounce-inches to pound-inches, which is a different unit pair entirely.
- Is lb-in the same as in-lb? What about lb-ft and ft-lb?
- Yes to both, and that's exactly why the fourth combination is dangerous. Torque is force times distance, and multiplication doesn't care about order, so lb-in and in-lb are the same unit, and lb-ft and ft-lb are the same unit. The trap is that lb-in and lb-ft look nearly identical — two characters apart — while being twelve times apart in size. A spec written 89 lb-in pulled to 89 lb-ft is roughly twelve times too tight, which on a valve cover bolt or an aluminum thread means a snapped fastener or a stripped hole. This tool accepts every inch-pound spelling and rejects foot-pound spellings with an error rather than guessing.
- What is an inch-pound in newton-meters?
- 0.112985 N·m. The chain is exact: one pound-force is 4.4482216152605 newtons (0.45359237 kg times 9.80665 m/s²) and one inch is 0.0254 m, so one lbf·in is 0.1129848290276167 N·m. Multiply by 12 and you get the familiar 1.3558 N·m per foot-pound. Metric service manuals almost always list N·m, so having the number sitting right next to the foot-pound answer saves a second lookup.
- My spec is in foot-pounds but my wrench only reads inch-pounds. Can I use it?
- Often, but check the range before you check the math. A click-type torque wrench is typically rated accurate to about ±4% across the top 80% of its scale, and meaningfully worse at the very bottom. So a 250 in-lb wrench asked for a 20 ft-lb spec (240 in-lb) is fine — you're near the top of its range. The same wrench asked for 40 ft-lb (480 in-lb) simply can't get there, and a 600 in-lb wrench asked for a 3 ft-lb spec (36 in-lb) is down at 6% of scale where the reading means very little. Convert first, then confirm the number lands inside the useful part of your wrench's range.
- Why are small fasteners specced in inch-pounds at all?
- Resolution. A valve cover bolt at 7.4 ft-lb is an awkward number to set and an easy one to misread; the same spec written as 89 in-lb is a clean integer on a clean scale. Anything under roughly 20 ft-lb tends to get published in inch-pounds for that reason, which is why electrical lugs, small engine covers, interior trim, bicycle components, and most electronics hardware use them while suspension and lug nuts use foot-pounds.
- Does hitting the torque number mean the bolt is tight enough?
- Torque is a proxy, not the goal. What actually holds a joint together is clamping load — the tension stretched into the bolt — and torque is just the easiest thing to measure from outside. Most of the torque you apply is spent overcoming friction under the head and in the threads, so anything that changes friction changes the clamp load you get from the same number. A lubricated or anti-seize'd thread can reach 20-30% more clamping load at the identical torque reading, which is enough to yield a fastener that would have been fine dry. Assume a spec is dry unless the manual says otherwise, and if it gives a lubricated figure, use that one.
- What about ounce-inches or kg-cm?
- Both are real torque units and neither is handled here, on purpose. Ounce-inches (oz-in) show up on small motors and instruments — 1 in-lb is 16 oz-in. Kilogram-force centimeters (kgf·cm) appear on older Japanese equipment — 1 in-lb is about 1.152 kgf·cm. Each needs its own explanation of which force is meant, and neither is what someone searching for inch-pounds to foot-pounds came for, so the converter names them in an error instead of silently treating them as inch-pounds.
- Is what I type saved or sent anywhere?
- No. The conversion runs in your browser. Nothing goes to a server, nothing is stored, and closing the tab clears it. Most converters like this one sit three clicks inside a site that wants an account and an email address first — this is just the converter.
