Engineering Intelligence.
Calculators for physics and engineering coursework and everyday checks — stress and strain, density, thermal expansion, Ohm’s law, unit conversion and statistics. SI units throughout, with the formula shown on every page.
Density Laboratory
Calculate ρ = m/V, or solve for mass or volume. Includes published reference densities for common materials, with output in kg/m³.
Launch ToolStress Analysis
Compute σ = F/A stress and strain, with a safety factor against the yield strength you enter.
Launch ToolUnit Metrology
Any-to-any conversion across length, mass, area, volume and temperature, using the exact factors defined by international agreement.
Launch ToolElectrical Lab
Compute voltage, current, resistance or power from any two known values.
Launch ToolSpeed / Distance / Time
Solve for speed, distance, or time given the other two values. Supports mph, km/h, m/s, miles, km, meters, and more.
Launch ToolTemperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine simultaneously. Edit any field and all four scales update in real time.
Launch ToolKinetic Energy
Calculate kinetic energy from mass and velocity in any unit. Results in joules, kilojoules, foot-pounds, and food calories.
Launch ToolStandard Deviation
Paste a list of numbers to instantly calculate mean, variance, and both population and sample standard deviation.
Launch ToolNot sure what a term means?
Stress, strain, Young's modulus, density, Ohm's Law, safety factor — all explained clearly.
Getting the Units Right Is Most of the Work
In physics and engineering problems the arithmetic is rarely what goes wrong. Units are. A calculation can be algebraically perfect and still produce an answer that is out by a factor of a thousand, and the result will look entirely plausible on the page.
Convert before you calculate, not after
The reliable habit is to put every quantity into base SI units first — metres, kilograms, seconds, pascals — run the calculation, then convert the answer into whatever unit you want to report. Mixing millimetres with metres inside a single expression is the most common source of an answer that is wrong by exactly 1,000 or 1,000,000, and those factors are large enough that they are usually caught. The dangerous errors are the small ones: grams for kilograms, or centimetres for metres, which produce answers wrong by 100 that can still look reasonable.
Check the dimensions of your answer
Before accepting a result, confirm its units are what the quantity should have. Stress must come out in pascals, which is newtons per square metre; if your working produces newtons per metre, you have divided by a length rather than an area. Density must be mass over volume. Kinetic energy must be in joules, which is kg·m²/s². This dimensional check catches a large share of algebraic mistakes without re-doing any of the arithmetic, because a dropped or duplicated term almost always changes the units.
Significant figures are a claim about precision
If you measure a beam as 2.4 m and a load as 500 N, your answer is not entitled to eight decimal places. Reporting it that way asserts a precision your inputs do not support. The working rule for multiplication and division is that the result carries as many significant figures as the least precise input — so two measurements to two significant figures give an answer to two. Our calculators display more digits than that because rounding mid-calculation introduces its own error; round once, at the end, to match your inputs.
Reference values are typical, not exact
Material presets — densities, expansion coefficients, moduli — are published typical values. Real materials vary with alloy composition, temper, moisture content and temperature, and published tables disagree with each other more than most people expect. Steel is not one number. For coursework a table value is the right input; for anything that gets built, use the figure on your supplier’s specification for the actual material and the actual temperature range.
Research & Notes.
In-depth articles on the math and logic behind our tools — written for people who want to understand the calculations, not just run them.
The Physics of Kinetic Energy: Why Speed Matters More Than Mass in a Crash
Kinetic energy scales with the square of velocity, not mass. That single mathematical fact explains why a modest increase in driving speed disproportionately increases crash severity and stopping distance.
Molecular Weight Variance in Lubricants: Why Viscosity Is Not a Single Number
When engineers specify a lubricant by viscosity grade, they are working with an average. The variance around that average determines how the oil actually behaves under pressure, heat, and shear.
Linear Thermal Expansion in Industrial Calibration: Why Temperature Changes Your Measurements
A 2°C temperature shift can move a precision measurement instrument outside its acceptable tolerance range. Here is the physics behind thermal expansion and how calibration labs account for it.