Engineering Calculators
Every engineering calculator on the site, in one place - electrical, mechanical, and structural tools, grouped by discipline.
Each tool shows its formula and a fully worked example directly on the page. Several - voltage drop, wire gauge, and beam load in particular - carry a note on where a calculator's estimate ends and a licensed professional's judgment should begin. Every calculation runs in your browser and nothing you enter is saved. Jump to a section, or scroll through all 15.
Electrical
Circuits, wiring, and components.
- Ohm's Law Calculator - voltage, current, resistance, and power from any two known values.
- Voltage Drop Calculator - voltage drop across a wire run, checked against standard guidance.
- Wire Gauge Calculator - the smallest wire gauge that keeps voltage drop within your target.
- Resistor Color Code Calculator - decode a 4-band or 5-band resistor's value and tolerance.
- LED Resistor Calculator - the correct current-limiting resistor for an LED circuit.
- Capacitor Calculator - stored energy and charge, or combined capacitance in series or parallel.
- Power Factor Calculator - power factor and reactive power for an AC electrical system.
Mechanical
Motion, force, and power transmission.
- Horsepower Calculator - horsepower from torque and RPM, or solve for torque instead.
- Torque Calculator - torque, force, or lever arm length from the other two.
- Gear Ratio Calculator - gear ratio, output speed, and torque multiplication from tooth counts.
Structural & fluid
Loads, flow, and pressure.
- Beam Load Calculator - maximum bending moment and support reactions for a simply supported beam.
- Flow Rate Calculator - volumetric flow rate from pipe diameter and fluid velocity.
- Pressure Converter - convert between PSI, bar, kPa, atmospheres, and mmHg.
Energy & HVAC
Heating, cooling, and solar sizing.
- BTU Calculator - estimated heating or cooling capacity needed for a room.
- Solar Panel Size Calculator - estimated solar system size and panel count from daily energy usage.
Frequently asked questions
Are these engineering calculators free to use?
Yes - all 15 tools on this page are free, with no account or sign-up required.
Can I use these for a real electrical or structural project?
These tools are built for learning, planning, and preliminary estimates using standard engineering formulas. For anything safety-critical - electrical wiring, structural beams, load-bearing work - always confirm with a licensed electrician or engineer and your local code, since real installations involve factors a general calculator can't fully account for.
Do I need an engineering background to use these?
No - each tool explains the formula and walks through a worked example in plain language, so they're useful for students, hobbyists, and professionals alike.
Is any of the information I enter saved?
No. Every calculation runs directly in your browser - nothing you type is sent to a server or stored anywhere.
Looking for a different category? Browse all calculators on the homepage. For articles and updates about these tools, see all Engineering Calculators posts.