Torque Calculator
Enter the values the torque form asks for and the result is computed here, in the page, with no sign-up and no upload. Change one field at a time to see how sensitive the torque figure is to that assumption.
Calculate Torque from Power & RPM
Calculate Torque from Force & Lever Arm
Calculate Bolt Tightening Torque
Use the scientific calculator with steps
Why Every Mechanic and Engineer Needs This Free Torque Calculator
If you’ve ever spent twenty minutes flipping through a shop manual just to convert 50 hp at 3000 rpm into newton‑meters, only to wonder whether a dry bolt needs a different friction factor than a lubricated one, you know the pain. That’s exactly why I started using the torque calculator on heycalc.org – and now it’s the only tool I open when I need a fast, reliable torque value.
This free online torque calculator does three things that used to require separate apps or a pocked‑out calculator: power‑torque‑RPM conversion, force‑lever‑arm torque, and bolt preload torque with friction factors. It works in both metric and imperial units (N·m, lb‑ft, kgf·m, and more) and gives instant results – no sign‑up, no uploads, no data leaving your device.
From Frustration to Flow: A Real‑World Story
Last week I was helping a friend select a motor for a small conveyor belt. We had the power rating (0.75 kW) and the desired shaft speed (200 rpm), but needed the torque to check the coupling’s rating. Instead of pulling out the formula books (T = 9550 × P / n), I just fired up the power‑torque‑RPM tab of this tool. Entered 0.75 kW, 200 rpm, clicked Calculate Torque – and within a second I had 35.8 N·m, plus the same value in lb‑ft and kgf·m. The visual torque vs RPM curve also showed me that if we ever needed to run at a lower speed, the torque would jump accordingly – a crucial insight for motor selection.
That’s the kind of thing that makes this more than a calculator: it’s a professional torque calculator that actually helps you understand what the numbers mean.
Three Calculation Modes, One Seamless Tool
1. Power → Torque → RPM (The “Which Motor Fits?” Use Case)
Whether you’re an automotive technician swapping an engine or a student designing a gearbox, the relation between power, torque, and rotational speed is the backbone of mechanical engineering. The power‑torque conversion in this tool handles both metric (kW) and imperial (hp), and gives you the angular velocity in rad/s as a bonus.
How to use it like a pro:
- Enter either power (kW or hp) and RPM.
- Hit Calculate Torque – you’ll see torque in N·m, lb‑ft, and kgf·m.
- The chart shows how torque changes with RPM (assuming constant power), so you can spot the sweet spot for your application.
This is especially handy when you’re reading motor datasheets that only list power and need to know the starting torque. Just plug in the numbers and you’ll have your answer before your coffee gets cold.
2. Force × Lever Arm (The “How Much Can I Lift?” Use Case)
Have you ever needed to know the torque applied by a wrench or a pedal? That’s the force‑lever torque calculation. It’s dead simple: torque = force × distance. But the tool makes it even simpler by letting you choose from multiple force units (newtons, kilogram‑force, pound‑force) and lever‑arm units (meters, cm, mm, feet, inches).
Pro tip for mechanics: If you’re tightening a bolt with a torque wrench that reads in lb‑ft, but the spec is in N·m, you can use this tab to convert the required force over a known arm length. Or if you’re designing a pedal, enter the force your foot applies and the pivot distance – the tool instantly shows torque in all common units. No mental math, no unit conversion errors.
3. Bolt Preload Torque with Friction (The “Will It Hold?” Use Case)
This is the calculator you didn’t know you needed – until the moment you overtighten a critical bolt and strip the threads. The bolt tightening torque tab uses the formula T = K × F × d, where K is the nut factor (friction coefficient). Most torque wrenches give you a torque value, but they don’t tell you how much friction affects the final clamp load. This tool does.
What you input:
- Bolt diameter (mm or inches)
- Desired preload force (N, kN, or lbf)
- K factor (typical: 0.10–0.15 for lubricated, 0.18–0.21 for dry)
What you get:
- Tightening torque in N·m and lb‑ft
- A recommended ±25% range (because real‑world friction is never perfect)
- A chart showing how torque scales with bolt diameter
This is invaluable for anyone assembling machinery, installing engine components, or working on structural joints. And because the tool runs entirely in the browser – no uploads, no backend – you can even use it for confidential engineering projects without worrying about data security.
Data Security: The “No Uploads” Promise That Actually Matters
I know what you’re thinking: “Another online tool that phones home with my data?” Not this one. Every calculation happens right inside your browser. Your motor specs, bolt sizes, and force values never leave your computer. That’s why I’m comfortable using it for my client work – and why it’s safe for students to use on university‑issued laptops without IT freaking out.
To put it plainly: there’s no server to hack, no database to scrape, and no privacy policy full of loopholes. The tool is as secure as the calculator app on your phone – but way more capable.
Final Thought: Why I Still Recommend It After Six Months
I’ve used dozens of torque calculators over the years – some are cluttered with ads, others require you to create an account, and a few are just plain inaccurate for bolt preload. This one hits a sweet spot: it’s free, it’s accurate, and it covers the three most common torque calculations in a clean interface. The fact that it’s also private makes it a no‑brainer for anyone who works with actual engineering data.
If you’re tired of double‑checking your hand calculations or digging up formulas from old textbooks, give the torque calculator on heycalc.org a try. It might just become your new go‑to – the same way it became mine.
Frequently Asked Questions about Torque Calculator
How do I sanity-check the torque result?
Rerun the calculator with a known example and compare it against the figure you expect; then swap back to your own numbers.
Which torque inputs change the outcome most?
Adjust one field at a time. The figure that shifts the result hardest is the assumption worth double-checking before you rely on it.
How do I calculate torque from horsepower and RPM using an online torque calculator?
Enter the horsepower (or kilowatt) value and the rotational speed in RPM into the Power‑Torque‑RPM tab of the tool. For the imperial system, the formula T (lb‑ft) = 5252 × P (hp) / n (rpm) is applied automatically, while metric uses T (N·m) = 9550 × P (kW) / n (rpm). The result appears instantly in multiple units.
What is the bolt tightening torque formula, and how does this tool handle friction?
The standard formula is T = K × F × d. In the tool’s Bolt Preload Torque section, you enter the bolt diameter (d), the desired clamping force (F), and the friction coefficient (K). Typical values for K are 0.10‑0.15 for lubricated threads and 0.18‑0.21 for dry. The tool calculates the recommended tightening torque and also shows a ±25% range to account for real‑world variation.
Is this torque calculator safe to use for confidential engineering work?
Absolutely. All calculations are performed locally in your browser – no data is sent to any server. You can input proprietary torque specs, bolt sizes from a protected motor design, or any other sensitive numbers without any risk of interception or storage. It’s as private as using a handheld calculator.
Can I convert torque units between N·m and lb‑ft with this tool?
Yes. Every calculation mode displays results in at least four units simultaneously: N·m, lb‑ft, kgf·m, and (for force‑lever) lb‑in. The bolt tab also shows N·cm. You never need to do a manual conversion – just read the value in the unit you need.