555 timer calculator
Calculate astable frequency and duty cycle or a monostable pulse, with component-tolerance bounds. Drag the graph handles to change inputs and explore the result.
Your inputs
The editable example is illustrative. Enter your own dimensions, operating data, prices, and fees. Results update as you edit.
Calculations run in your browser. Inputs are not saved or sent to analytics.
How it works
- High time = ln(2) × ( + ); Low time = ln(2) × ; f = 1 / (High time + Low time); Pulse width = ln(3) ×
Input and formula key
Your result
Complete the inputs to see your result.
Assumptions and limitations
Uses the conventional two-resistor astable or one-resistor monostable circuit. Duty cycle means output-high time. Bounds combine component extremes only, excluding IC and parasitic errors. Verify practical limits in the chosen device datasheet. Example: R₁ 10 kΩ, R₂ 100 kΩ and C 10 µF give about 0.687 Hz and 52.38% high duty.
Sources
- Texas Instruments — NE555 datasheet, astable and monostable operation Sources reviewed: 2026-10-22
