555 timer
Calculate, convert and check circuit values in your browser.
Inputs
Results
- Time
- 0.011 s
Formula and assumptions
tmono ≈ 1.1R₁C; thigh = ln(2)(R₁+R₂)C; tlow = ln(2)R₂C; f = 1/(thigh+tlow)
Questions, examples and engineering limits
Calculate 555 pulse width, frequency, high/low times and duty cycle. Understand the standard astable circuit’s 50% limit and component tolerances.
Content updated:
How is 555 Timer Calculator: Monostable and Astable Timing calculated?
Use tmono ≈ 1.1RC; f ≈ 1/[ln(2)(R₁+2R₂)C]. Calculate 555 pulse width, frequency, high/low times and duty cycle. Understand the standard astable circuit’s 50% limit and component tolerances.
Sources: ti.com [1]
How do I calculate this example: R = 10 kΩ, C = 1 µF (monostable)?
t ≈ 11 ms. This is a calculated example under the model stated above; it is not a measured component specification.
Which units does 555 Timer Calculator: Monostable and Astable Timing use?
Ω, F, s, Hz, %. Convert prefixes before substituting values; keep the input and output units attached to every number.
Sources: ti.com [1]
Can the standard astable circuit have duty below 50%?
Not with positive R₁ and R₂ in this topology: duty = (R₁+R₂)/(R₁+2R₂). Diode-steered variants require different equations.
Sources: ti.com [1]
Why does measured frequency differ from the calculator?
Capacitor leakage, tolerances, threshold errors and discharge behavior affect timing. Check the exact bipolar or CMOS timer datasheet.
Sources: ti.com [1]
Does this validate every possible 555 frequency?
No. Mathematical output does not verify supply range, minimum pulse width, discharge current or the operating frequency of a specific IC.
Sources: ti.com [1]
Answers use the stated model and units. Examples are calculated values, not measurements or component ratings.