Electronics & Embedded
Calculators for makers, hobbyists, and embedded engineers
A focused set of fast, browser-side electronics calculators: Ohm’s law, resistor color codes, LED dropping resistors, voltage dividers, RC time constants, 555 timers, ADC/DAC, and PWM. Engineering notation throughout, no sign-up, nothing uploaded.
All Electronics & Embedded
Ohm’s Law Calculator
Solve Ohm’s law for voltage, current, resistance, or power. Enter any two of V, I, R, and P and instantly get the other two with step-by-step derivations.
Power Calculator (DC, AC, 3-Phase)
Compute real, apparent, and reactive power for DC and AC circuits including single-phase and three-phase systems with adjustable power factor.
Resistor Color Code Decoder
Decode and encode 3, 4, 5, and 6-band resistor color codes. Pick colors to read the value, or enter a value to see the matching color bands.
LED Resistor Calculator
Size the current-limiting resistor for a single LED, an LED chain in series, or several LEDs in parallel. Picks the nearest standard E-series value and recommends a safe wattage rating.
Voltage Divider Calculator
Calculate the output voltage, current, and power of a resistive voltage divider with optional load. Highlights loading effects when the load is too small.
RC Time Constant Calculator
Compute the time constant τ = R × C, plot the charge or discharge curve, and find the time to reach a target voltage for any RC circuit.
Capacitor Charge & Energy Calculator
Compute the stored charge (Q = CV) and energy (E = ½ CV²) of a charged capacitor, with intuitive real-world comparisons.
555 Timer Calculator
Design an NE555 astable oscillator or monostable one-shot. Pick R1, R2, C and read off frequency, period, duty cycle, and pulse width, with an inline schematic.
ADC / DAC Converter Calculator
Convert between analog voltage and digital code for any N-bit ADC or DAC. Computes LSB size, quantisation error, full-scale range, and ideal dynamic range (SQNR).
PWM Duty & Frequency Calculator
Solve any unknown of a PWM waveform: frequency, period, duty cycle, on-time, off-time. Optional supply voltage gives average and RMS voltage. Inline waveform preview.
Motor Full Load Current Calculator
Compute motor full-load current (FLA / FLC) for DC, single-phase, and three-phase motors from horsepower or kilowatts, efficiency, and power factor. Side-by-side NEC 430.250 reference.
Power Factor Correction Calculator
Compute kVAR and capacitance per phase needed to raise an installation from its current power factor to a target. Before/after power-triangle diagram and current-reduction estimate.
Short Circuit Current Estimator
Educational point-to-point estimator for available short-circuit current from a transformer secondary, with optional cable attenuation. Not a replacement for IEEE 1584 or utility-provided fault values.
UPS Runtime Calculator
Estimate UPS / battery-backup runtime from battery voltage, capacity, series / parallel arrangement, load wattage, inverter efficiency, and depth of discharge. Includes a Peukert warning at high discharge rates.
Conduit Fill Calculator
NEC Chapter 9 conduit-fill calculator. Pick conduit type and trade size, add cables (THHN/THWN/XHHW by AWG), and get utilisation, NEC limit, and pass/fail.
Voltage Drop Calculator
NEC voltage drop calculator. Enter system, voltage, current, one-way length and conductor, and get volts dropped, percent drop, voltage at the load and the smallest conductor that meets your target.
Wire Size Calculator
NEC wire size calculator. Sizes copper or aluminum against Table 310.16 ampacity with ambient and conduit-fill derating, then against your voltage drop target, and reports which limit decided it.
Signal Attenuation (dB) Calculator
Convert between power / voltage ratios and dB, compute Free-Space Path Loss (FSPL), and estimate cable attenuation. Supports forward and reverse calculations.
Transformer Sizing Calculator
Compute required transformer kVA from connected load, power factor, future growth, K-factor (harmonics), and ambient derating. Picks the next NEMA standard rating.
Cable Tray Fill Calculator
NEC 392.22 cable tray fill check for ladder, ventilated, and solid-bottom trays. Sums cable areas / diameters and reports pass/fail with the right rule citation.
Generator Sizing Calculator
Size a standby or prime generator from continuous load, largest motor (HP + NEMA code letter + start method), altitude and ambient derating. Picks the next standard kW rating.
What is in Electronics & Embedded
These are the calculators an electrician, an electronics hobbyist or a controls engineer reaches for during design rather than after it. About half answer code questions: conduit and cable tray fill against NEC Chapter 9 and 392.22, motor full load current against Table 430.250, and transformer and generator sizing against the standard ratings you can actually order. The rest are bench arithmetic: Ohm's law, resistor color codes, LED dropping resistors, RC time constants, 555 timing, ADC resolution and PWM duty.
Every one runs in your browser and accepts engineering notation, so you can type 4k7 or 100n and get a sensible answer back in the same style. Nothing is uploaded and nothing is stored, which matters when the numbers describe a client's installation.
They are sizing aids, not permit documents. The code calculators name the table or section they apply and show every intermediate area and current, so you can check the working against your own printed code book before anything is installed.
Common questions
Are these calculators code compliant?
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They apply the published NEC tables, cite the section used, and show every intermediate value so the working can be checked. They are sizing aids for design work, not permit documents. Always cross-check against your own current code book, and remember that local amendments override the national text.
Which NEC tables do the numbers come from?
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Conduit and conductor areas follow Chapter 9 Tables 1, 4 and 5, cable tray fill follows 392.22, and motor currents follow Table 430.250. Each tool states the table it uses so you can confirm it against the edition your jurisdiction has adopted.
Can I type values in engineering notation?
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Yes. Inputs accept shorthand like 4k7, 100n and 2M2 alongside plain numbers and exponent notation, and results come back in the same style rather than as a wall of decimal places.
Does anything I enter leave my browser?
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No. Every calculator in this category is client side. There is no upload, no account and no logging, so figures describing a real installation stay on your machine.