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555 timer calculator
Frequency, duty cycle and timing for a 555 timer in astable or monostable mode.
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About 555 timer calculator
Calculate frequency, duty cycle and timing for the classic 555 timer from its resistor and capacitor values. In astable mode, frequency is about 1.44 divided by (R1 plus 2 times R2) times C. In monostable mode, the pulse length is about 1.1 times R times C.
How to use 555 timer calculator
- Enter your numbers above.
- The result updates instantly as you type.
- Change any value to compare different cases.
Why use this tool?
- Private: everything happens in your browser. Nothing you enter is uploaded.
- Free, with no sign-up, no watermark and no limit on how often you use it.
- Works on phones, tablets and computers: Android, iPhone, Windows, Mac and Linux. Nothing to install.
- Available in 10 languages.
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Frequently asked questions
Why can't a 555 astable have 50 percent duty cycle?
Because the capacitor charges through R1 plus R2 but discharges only through R2, the high time is always longer than the low time.
Is 555 timer calculator free?
Yes. 555 timer calculator on Toolipedia is free to use, with no sign-up and no watermark.
Is it safe to use?
Yes. Everything is worked out in your browser, and nothing you enter is sent to our server.
Does it work on my phone?
Yes. It works in any modern browser on Android and iPhone, as well as on tablets and computers. There's nothing to install.
Do I need an account?
No. Just open the page and use the tool. There's no sign-up and no email needed.