Arduino Uno Pinout & Pin Capability Reference
Filterable Uno pin table — PWM timers, SPI/I²C roles, interrupts and the current limits that silently kill projects.
Arduino Uno Pinout Reference computes the Uno/ATmega328P pin map with PWM timers, buses, interrupts and current limits — free, instant and private in your browser. Arduino learners and teachers mapping projects onto the right pins 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 Uno Pinout & Pin Capability Reference
Arduino Uno Pinout Reference computes the Uno/ATmega328P pin map with PWM timers, buses, interrupts and current limits using the standard engineering relation: PWM on 3,5,6,9,10,11; SPI 10–13; I²C A4/A5; INT0/1 on 2/3; 20 mA per pin, 200 mA total. Worked live: changing Timer0's PWM frequency silently breaks millis() and delay() — retune Timer1 or 2 instead. 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 Uno Pinout & Pin Capability Reference
- 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 Uno Pinout & Pin Capability Reference?
- ✓Implements the real formula — PWM on 3,5,6,9,10,11 — with the substitution shown, not a black box
- ✓Built for Arduino learners and teachers mapping projects onto the right pins
- ✓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 uno pinout?+
The Uno/ATmega328P pin map with PWM timers, buses, interrupts and current limits follows PWM on 3,5,6,9,10,11; SPI 10–13; I²C A4/A5; INT0/1 on 2/3; 20 mA per pin, 200 mA total. For example, changing Timer0's PWM frequency silently breaks millis() and delay() — retune Timer1 or 2 instead. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why are pins 5 and 6 brighter (faster PWM) than 9 and 10?+
Different timers: 5/6 ride Timer0 at ~976 Hz, 3/9/10/11 ride Timers 1/2 at ~490 Hz. Timer0 also runs the millis() clock, which is why its frequency is left alone and why analogWrite duty on 5/6 has slight asymmetry at the extremes.
How many LEDs can the Uno drive directly?+
Respect three budgets: 20 mA recommended per pin (40 abs max), 100 mA per port group, 200 mA for the whole chip. Eight LEDs at 20 mA already nominally short the chip budget — at 5 mA each modern LEDs are plenty bright and everything stays comfortable.
Is the Arduino Uno Pinout Reference 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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