Mechanical Engineering Calculators
These calculators cover machine design and the workshop: converting torque, power and speed, working out gear and pulley ratios, tightening bolts to the right preload, sizing compression springs, checking axial stress against yield, estimating bearing life, sizing hydraulic cylinders, choosing tap drills and setting spindle speeds and feed rates.
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All Mechanical (10)
Torque and Power Calculator
Convert between torque, power and speed in metric and imperial unitsGear Ratio Calculator
Gear ratio, output speed and torque for gear trainsPulley and Belt Calculator
Pulley speeds, belt length and belt speed for two-pulley drivesBolt Torque Calculator
Tightening torque and preload for metric and UNC/UNF boltsSpring Calculator
Rate, stress and deflection of helical compression springsStress and Strain Calculator
Stress, strain, Young's modulus and elongation under axial loadBearing Life Calculator
L10 rating life of ball and roller bearings from load and speedHydraulic Cylinder Calculator
Cylinder force, speed and flow from bore, rod and pressureTap Drill Size Calculator
Tap drill size and thread engagement for metric and unified threadsSpeeds and Feeds Calculator
Spindle RPM and feed rate for milling, drilling and turning
Which tool do I need?
Find the tightening torque for a bolt
Pick the size and property class and the lubrication condition to get the torque and the clamping force it produces.
Work out the output speed of a gearbox
Enter the tooth counts of each gear pair to get the overall ratio, output speed and torque.
Set the spindle speed for an end mill
Pick the material and tool, enter the diameter and teeth, and read the rpm and feed rate.
Choose the drill for a tapped hole
Pick the thread and the engagement you want to get the drill size and the engagement a standard drill gives.
About Mechanical
Each tool states its source, such as ISO 898-1 proof loads for bolts, ISO 281 for bearing life and Machinery's Handbook style starting values for cutting speeds, and keeps the units straight between newton-metres and pound-feet, bar and psi, metres per minute and surface feet per minute.
Results are for checking, learning and preliminary design. Anything that carries load, current, pressure or people must be confirmed by a qualified engineer or licensed tradesperson against the code that governs your project.
Guides
- Torque, Horsepower and RPM: Where 5252 and 9549 Come FromP = T x ω explained from first principles, the origin of the 5252 and 9549 constants, mechanical versus metric horsepower, and how to read motor nameplates and dyno charts without unit errors.
- Gear Train Ratios Explained: Simple, Compound, Idlers and LossesWhy tooth counts set the speed ratio, why compound ratios multiply and idlers cancel, how torque and efficiency carry through a train, and the tooth-count rules that keep gears quiet and long-lived.
- Belt Length and Pulley Speed Formulas, Derived and CheckedThe exact open-belt length formula from tangent geometry, where the handbook approximation comes from and when it drifts, wrap angle and slip, and how to go from a stock belt back to centre distance.
- Bolt Tightening Torque and Preload: T = KFd in PracticeHow proof load, stress area and nut factor set the torque for metric and inch bolts, why K matters more than the wrench, how much preload a joint needs, and when torque alone is not good enough.
Frequently asked questions
Why does lubrication change the bolt torque so much?
Most tightening torque is lost to friction under the head and in the threads. Lubrication lowers the nut factor, so the same torque produces much more preload and can overload the bolt if the dry value is used.
Is a bearing's L10 life a guaranteed service life?
It is the life that 90% of a large group of identical bearings will reach or exceed under the same conditions. It is a statistical rating, not a guaranteed life for one bearing.
How do I convert between torque and horsepower?
Horsepower equals torque in pound-feet times rpm divided by 5,252. In SI units, power in watts equals torque in newton-metres times angular speed in radians per second.
What thread engagement should a tapped hole have?
About 65 to 75% is common. Higher engagement adds little strength but makes tapping much harder and breaks more taps, especially in tough materials.