Calculators

Electronics calculators

Each one updates as you type and runs in your browser. The formulas are the ones the lessons are checked against, and every page links down to the lessons that explain the answer.

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• Resistor color code calculator

  Bands to ohms and ohms to bands, with the tolerance range and the nearest standard value.

  Background: The resistor colour code

• LED resistor calculator

  One LED or a string: exact and standard resistor, real current, resistor wattage.

  Background: LED circuits

• Voltage divider calculator

  Loaded and unloaded output, tolerance spread, and the best standard pair for a target.

  Background: The voltage divider

• Capacitor code calculator

  Printed code to pF, nF and µF with tolerance and voltage, and a value back to its code.

  Background: Capacitor markings

• SMD resistor code calculator

  Three-digit, four-digit, R and EIA-96 codes both ways, with checks on what you typed.

  Background: SMD resistor codes

• LM317 calculator

  R1 and R2 both ways, headroom, dissipation, heatsink, and the one-resistor current source.

  Background: Linear regulators

• Inverter battery backup calculator

  Backup hours for a home inverter, or the battery size a target time needs.

  Background: Battery types

• 555 timer calculator

  Astable and one-shot timing, a waveform to scale, and RA and RB for a target frequency.

  Background: The 555 timer

• RC time constant calculator

  τ, voltage at any time, time to a target, R for a delay, with tolerance and leakage.

  Background: The RC time constant

• Standard resistor combination finder

  Hit an odd value with two or three standard parts, from a series or from the parts you have.

  Background: Series circuits

• RC snubber calculator

  Damp switch-node ringing: Lpar and Cpar from the scope, then Rs, Cs and the watts.

  Background: Series RLC circuits

• Skin depth calculator

  Skin depth, then the real AC resistance of your wire, its loss in watts and the largest litz strand.

  Background: Skin effect

Pages that use these numbers

Some answers need a part's own limits as well as a formula. These pages pair the two.

• AMS1117 regulator: why it needs up to 1.4 V of headroom, and the heat it makes from 12 V in.
• IRFZ44N vs IRLZ44N: the gate voltage each one is rated at (10 V, or 5 V and 4 V), and when a swap works.
• How many times will a power bank charge my phone? Charges and refill time, worked out from the labels.

Looking for the AI tools, such as Datasheet Guru? They live under tools. Author of the calculators: Bulan Sarkar. Found a wrong number? Tell us.