FREE · CONSTRUCTION & TRADE CALCULATORS
555 Timer Calculator.
Calculate the frequency, duty cycle and timing of a 555 astable oscillator or the pulse of a monostable, or design the resistors for a frequency.
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How to use 555 Timer Calculator
Choose astable, monostable or design mode, enter the resistors in kΩ and the capacitor with its unit. Design mode returns the nearest E24 resistors.
How it works
Astable: f = 1.44 ÷ ((R1 + 2R2) × C); high time 0.693 (R1 + R2) C; low time 0.693 R2 C. Monostable: t = 1.1 R C.
Example
R1 = 1 kΩ, R2 = 10 kΩ and C = 10 nF oscillate at 6.871 kHz with a 52.4 % duty cycle.
Questions about 555 Timer Calculator
Is 555 Timer Calculator free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
Classic NE555 formulas; CMOS versions are close. Capacitor tolerance usually dominates the error. Everything is calculated in your browser; nothing you type is uploaded. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.