Timer Prescaler Calculator
Best prescaler + compare value for any target period — searches the AVR set or powers of 2, with exact error shown.
Choose the SMALLEST prescaler that fits: finer ticks mean less rounding error and better ISR jitter granularity. For “1 second” class periods on 8-bit timers, let the timer fire every 10 ms and count 100 interrupts in software. Remember compare = counts − 1: the timer counts 0..compare inclusive — the classic off-by-one.
Timer Prescaler Calculator computes the best prescaler + compare value for any timer period — free, instant and private in your browser. Firmware authors setting interrupt rates and timeouts in registers 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 Timer Prescaler Calculator
Timer Prescaler Calculator computes the best prescaler + compare value for any timer period using the standard engineering relation: T = N·(compare+1)/f(clk) — searched over the AVR set or powers of two. Worked live: 100 ms at 16 MHz: prescaler 64, compare 24999 — exact to the tick. 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 Timer Prescaler 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 Timer Prescaler Calculator?
- ✓Implements the real formula — T = N·(compare+1)/f(clk) — searched over the AVR set or powers of two — with the substitution shown, not a black box
- ✓Built for firmware authors setting interrupt rates and timeouts in registers
- ✓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 timer prescaler?+
The best prescaler + compare value for any timer period follows T = N·(compare+1)/f(clk) — searched over the AVR set or powers of two. For example, 100 ms at 16 MHz: prescaler 64, compare 24999 — exact to the tick. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Which prescaler should I prefer when several fit?+
The smallest: finer tick granularity means less rounding error in the period and finer-grained adjustments later. The only reasons to go bigger are fitting a long period into the counter width or sharing the prescaler with another channel's needs.
How do I make seconds-long periods on an 8-bit timer?+
Don't chase huge prescalers — fire a comfortable interrupt (say 10 ms) and count 100 of them in software. It's exact, portable and keeps the ISR trivial. Timer chaining works too but costs a second timer and readability.
Is the Timer Prescaler 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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