Electrical Calculators

Electrical Calculators cover the work from the service panel to the circuit board. Size wire, check ampacity and voltage drop, and fill boxes and bend conduit. Size motors, transformers, and generators, then design RF, antenna, and PCB circuits.

Wiring & Installation

11 calculators

Wire size, ampacity, voltage drop, box fill, and conduit bends.

See all Wiring & Installation calculators

Power, Energy & Batteries

13 calculators

Ohm's law, watts, kWh cost, RMS voltage, and battery runtime.

See all Power, Energy & Batteries calculators

Motors, Generators & Transformers

8 calculators

Full-load amps, speed, torque, kVA, and fault current.

See all Motors, Generators & Transformers calculators

Resistors, Capacitors & Inductors

13 calculators

Color codes, parallel networks, reactance, and time constants.

See all Resistors, Capacitors & Inductors calculators

Amplifiers, Timers & Filters

6 calculators

Op-amp gain, hysteresis, 555 timing, and bandpass design.

See all Amplifiers, Timers & Filters calculators

PCB & Transmission Lines

13 calculators

Microstrip and stripline impedance, trace width, and crosstalk.

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RF Links & Antennas

9 calculators

EIRP, path loss, link margin, noise figure, and patch antennas.

See all RF Links & Antennas calculators

RF Components & Matching

11 calculators

VSWR, attenuator pads, matching, dividers, and waveguide.

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Waves, Fields & Optics

7 calculators

Wavelength, decibels, skin depth, refraction, and beam power.

See all Waves, Fields & Optics calculators

How These Electrical Calculators Are Grouped

Electrical Calculators here run from the service panel to the circuit board. The nine categories above follow the work itself, so each one holds the tools a single job actually needs.

Pick the category that matches your task, then open the tool. Every category page lists its tools with a line on what each one works out.

Category	What it answers
Wiring & Installation	Wire size, ampacity, voltage drop, box fill, conduit bends
Power, Energy & Batteries	Ohm's law, watts, kWh cost, RMS voltage, battery runtime
Motors, Generators & Transformers	Full-load amps, speed, torque, kVA, fault current
Resistors, Capacitors & Inductors	Color codes, networks, reactance, time constants, resonance
Amplifiers, Timers & Filters	Op-amp gain, hysteresis, 555 timing, passband and Q
PCB & Transmission Lines	Microstrip and stripline impedance, trace width, crosstalk
RF Links & Antennas	EIRP, path loss, link margin, noise figure, patch antennas
RF Components & Matching	VSWR, attenuator pads, matching, dividers, waveguide
Waves, Fields & Optics	Wavelength, decibels, skin depth, refraction, beam power

Installation Work and Design Work

The first three categories cover installed systems. They answer questions with conductors, boxes, raceways, and machines in them, and their limits come from adopted code.

The next three cover circuit design. Values there come from component data sheets and target performance, not from code tables, so the constraint is what you can buy and what fits.

The last three cover signals at high frequency, where a trace becomes a transmission line and loss gets counted in decibels. Those tools share the same maths as the RF and microwave work above them.

Codes and Standards Behind the Numbers

Installation tools follow the National Electrical Code, NFPA 70. The tables and articles that come up most are 310.16 for ampacity, 240.4(D) for small conductors, 314.16 for box fill, 314.28 for pull boxes, 358.26 for total bends, and Article 430 for motors.

One thing to know about the NEC. It is republished every three years, and the 2026 edition arrived in late 2025. Adoption happens state by state, often years later and with local amendments, so several states are still enforcing the 2020 or 2017 edition. Your inspector's edition is the one that counts.

Board and cable work follows other documents. IPC-2141 covers controlled impedance, IPC-2221 covers trace width for current, and RF link figures come from the Friis equation and ITU propagation models. Decibel definitions follow IEC and ISO practice.

Every tool shows the formula and the values behind its answer, which makes a result easier to defend in a review or explain on site.

Where to Start

Running a circuit. Start with wire size, then check voltage drop over the real run length, then box fill and bend marks.

Sizing equipment. Get motor full-load amps or transformer kVA first, then the fault current the gear must interrupt.

Designing a circuit. Set gain, timing, or filter values, then find the nearest standard component and recheck the result.

Laying out a board. Hit the target impedance from the stackup, then size traces for current and check crosstalk at your rise time.

Planning a radio link. Work out EIRP and path loss, then compare received power with sensitivity to see the margin.

Units That Get Mixed Up

Most wrong answers come from units rather than arithmetic. Four pairs cause the majority of them.

Pair	Difference
kW and kVA	Real power against apparent power; equal only at unity power factor
dB and dBm	A ratio against a level referenced to 1 mW
RMS and peak	Peak is 1.414 times RMS on a sine wave
AWG and mm²	Gauge numbers run backward; larger AWG means thinner wire

Each tool states its units on every input, and the conversion tools handle the rest.

Electrical Calculator FAQs

Are these calculators based on the NEC?

The installation tools are, and they name the article behind each result, such as 310.16 for ampacity or 314.16 for box fill. Circuit, PCB, and RF tools follow other standards instead, mainly IPC documents and standard transmission-line and link-budget equations. Either way, results are for planning and checking, and the adopted code plus your inspector decide what gets installed.

Which NEC edition applies to my job?

Whichever one your jurisdiction has adopted, not the newest one published. NFPA issues a new edition every three years, and the 2026 edition came out in late 2025, but states adopt on their own schedules and add amendments. Several are still on 2020 or 2017. Check with your state electrical board or local authority before relying on an edition-specific rule.

Can I use these results for a permit or inspection?

Use them to plan, to check your own numbers, and to catch errors before the wall closes. Final conductor sizes, protection settings, and enclosure choices follow the adopted code, the equipment listing, and your inspector's judgement. Because each tool shows its formula and inputs, walking an inspector through a calculation is straightforward.

Do the tools handle single-phase and three-phase?

Yes, and DC where it applies. The three-phase forms add the square root of three, about 1.732, and use line-to-line voltage with line current. That factor is the usual source of errors, since dropping it overstates current by 73% on a three-phase load.

Do they work in metric as well as US units?

Both. Wire sizes convert between AWG and mm², lengths accept feet or metres, and RF and PCB tools take mils or millimetres. Keep one system within a single calculation, then convert at the end, since mixing inches and millimetres mid-calculation is the most common unit mistake in board and conduit work.

Which calculator should I use for a long circuit run?

Two, in order. Wire size gives the conductor the load needs, then voltage drop checks whether that conductor still delivers usable voltage at the far end. Long runs are decided by the second check, so a 20 A circuit can pass on 12 AWG at 40 ft and need 10 AWG at 120 ft with the same breaker.