ElectroCalculators
Free electronics & electrical engineering calculators

Electronics & electrical calculators

Interactive tools for circuit design and electrical installation. Type values the way you write them on a schematic — 4k7, 100n, 20m — and get standard component values, power ratings and worked examples alongside every result.

Free calculators
8
Standards
IEC / IEEE
Registration
None
Engineering input
4k7

8 calculators

Ω

Ohm’s Law

Solve for voltage, current, resistance or power. Get all four values at once, plus the resistor wattage you actually need.

R1R2

Voltage Divider

Calculate output voltage, ratio, current and output impedance — with the loading effect built in, not hidden on another page.

W

Power & Energy

Power from any two of voltage, current and resistance — then energy in kWh and what it costs to run.

4-6

Resistor Color Code

Decode 4, 5 and 6-band resistors, or enter a value to see its bands. Tolerance range and temperature coefficient included.

104

Capacitor Code

Decode ceramic capacitor markings — 104 is 100 nF, not 104 of anything — or work backwards from a value to the printed code.

LED

LED Resistor

Size the current-limiting resistor for any LED. Rounds up to the nearest E24 value, because rounding down overdrives the LED.

ΔV

Voltage Drop

Voltage drop for DC, single-phase and three-phase runs in copper or aluminium, sized in mm² or AWG, checked against IEC and NEC limits.

AWG

AWG Wire Gauge

Diameter, cross-section, resistance and current rating for any AWG size — with separate free-air and in-conduit ampacity, because they differ by a factor of two.

Browse by category

Each hub collects the calculators for one area, with the background you need to choose between them.

  • Basics — Ohm’s law, power, voltage dividers and the fundamental relationships every circuit rests on.
  • Resistors & Components — Colour codes, component codes, power ratings and standard-value selection for real parts.
  • Power & LED — Regulators, LEDs, batteries, thermal design and switching converters.
  • Electrical & Installation — Cable sizing, voltage drop, three-phase power and motor calculations to NEC and IEC.

Why ElectroCalculators?

  • Engineering notation input. Type 4k7, 2M2 or 100n directly — no unit dropdowns to fight with.
  • Standard component values. Every computed resistor or capacitor value is snapped to the nearest E-series part, with the resulting error shown.
  • Power ratings, not just numbers. Results include the dissipation and the wattage you should actually specify.
  • Shareable and embeddable. Every result has its own URL, and every calculator can be embedded in your own site.
  • Verified formulas. Cross-checked against IEC, IEEE and NEC and standard reference texts, with unit tests against textbook worked examples.