Peripheral Clock Divider Calculator
Integer divider for any target frequency from your clock tree — achieved frequency, error and the reachable neighbours.
Integer division is why some frequencies are simply unreachable: 80 MHz can make exactly 400 kHz (÷200), but 80 MHz → 3 MHz SPI gives ÷27 = 2.96 MHz. When the error matters (audio sample rates, CAN bit timing), use a fractional divider/PLL if the chip has one — or pick a crystal that divides cleanly. Slower bus clocks are always safe; faster rarely is.
Clock Divider Calculator computes the integer divider that gets closest to a target peripheral frequency — free, instant and private in your browser. Embedded developers configuring SPI/I²C/CAN clocks from the system tree 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 Peripheral Clock Divider Calculator
Clock Divider Calculator computes the integer divider that gets closest to a target peripheral frequency using the standard engineering relation: f(out) = f(in)/N; N = round(f(in)/f(target)), error reported. Worked live: 80 MHz to I²C-400 kHz divides exactly (÷200); 80 MHz to 3 MHz SPI lands on 2.96 MHz (÷27). 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 Peripheral Clock Divider 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 Peripheral Clock Divider Calculator?
- ✓Implements the real formula — f(out) = f(in)/N — with the substitution shown, not a black box
- ✓Built for embedded developers configuring SPI/I²C/CAN clocks from the system tree
- ✓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 clock divider?+
The integer divider that gets closest to a target peripheral frequency follows f(out) = f(in)/N; N = round(f(in)/f(target)), error reported. For example, 80 MHz to I²C-400 kHz divides exactly (÷200); 80 MHz to 3 MHz SPI lands on 2.96 MHz (÷27). The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Is running a bus slower than spec ever a problem?+
Almost never — I²C, SPI and UART all tolerate slower clocks; only minimum-frequency parts (some dynamic logic, certain ADC clocks) care. Slower is the safe direction when the divider can't hit the target exactly; faster than spec is where corruption begins.
My exact frequency is unreachable — what are my options?+
Fractional dividers or PLLs if the chip has them (audio and CAN usually need this), choosing a crystal that divides cleanly (the 14.7456 MHz trick generalises), or accepting the nearest integer and checking the protocol's tolerance — CAN wants < 0.5 %, I²C doesn't care.
Is the Clock Divider 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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