Design a 555 blinker without the datasheet algebra
Two resistors and a capacitor set the blink rate. Try R and C for a target frequency, or read the duty cycle you already have.
Tools used in this guide
The job
In astable mode a 555 charges C through R1+R2 and discharges through R2: f = 1.44/((R1+2R2)·C), and the duty cycle is (R1+R2)/(R1+2R2) — always above 50%. Monostable mode outputs one pulse of 1.1·R·C per trigger.
Two directions
Enter R1, R2, C to get frequency, duty, and high/low times — or enter a target frequency and capacitor and let the solver pick E24 resistor values.
Worked example
R1 = 1 kΩ, R2 = 6.8 kΩ, C = 100 nF blinks at 986 Hz with 53.4% duty — high 540 µs, low 471 µs. Solving for 1 kHz with C = 10 nF picks R1 = 8.2 kΩ, R2 = 68 kΩ (998.6 Hz, off by 0.0014%). For a 5-second monostable pulse with 47 µF, the tool returns R ≈ 96.7 kΩ.
Scope
Resistors 100 Ω–100 MΩ, capacitors 100 pF–10,000 µF; astable targets 0.01 Hz–500 kHz, monostable pulses 1 µs–3600 s. Real 555s have leakage and tolerance — the solver's percentage error is against ideal math.