Arduino LED Resistor Calculator
Why every Arduino tutorial says 220 Ω — pin current limits, the 40 mA myth and safe multi-LED fan-out from 5 V logic.
Preset: 1 red LED from a 5 V pin at 10 mA → 330 Ω next-up. The chip budget is ~150 mA TOTAL across all pins — divide it before you wire eight 20 mA LEDs to a poor ATmega.
Arduino LED Resistor Calculator computes the right series resistor from a 5 V Arduino pin — and the per-chip current budget behind it — free, instant and private in your browser. Arduino beginners and educators wiring their first (and fiftieth) LED use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Arduino LED Resistor Calculator
Arduino LED Resistor Calculator computes the right series resistor from a 5 V Arduino pin — and the per-chip current budget behind it using the standard engineering relation: R = (Vs − Vf)/If from 5 V logic; 220 Ω → 13.6 mA, 330 Ω → 9 mA, 1 kΩ → 3 mA on red. Worked live: one red LED at 10 mA wants (5−2)/0.01 = 300 Ω → 330 Ω E24. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Arduino LED Resistor Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Arduino LED Resistor Calculator?
- ✓Implements the real formula — R = (Vs − Vf)/If from 5 V logic — with the substitution shown, not a black box
- ✓Built for Arduino beginners and educators wiring their first (and fiftieth) LED
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate arduino led resistor?+
The right series resistor from a 5 V Arduino pin — and the per-chip current budget behind it follows R = (Vs − Vf)/If from 5 V logic; 220 Ω → 13.6 mA, 330 Ω → 9 mA, 1 kΩ → 3 mA on red. For example, one red LED at 10 mA wants (5−2)/0.01 = 300 Ω → 330 Ω E24. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Is the famous 40 mA per pin safe to use?+
No — 40 mA is the ATmega328's ABSOLUTE MAXIMUM (damage threshold), not an operating spec. Design at ≤20 mA per pin, and watch the real limit: ~200 mA for the entire chip. Eight LEDs at 20 mA already crowds it; at 10 mA each you're comfortably inside.
What if I need to drive more LEDs than the chip budget allows?+
Hand the current to something else: a 74HC595 shift register per 8 LEDs (mind its own 70 mA package budget), transistor or MOSFET drivers for power LEDs, or dedicated LED-driver ICs with constant-current outputs. The Arduino then spends microamps of signal instead of milliamps of muscle.
Is the Arduino LED Resistor Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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