Free online calculator

Pull-up resistor calculator

Open the calculator

Logic

Example Use 27 kΩ (valid range 825 Ω to 990 kΩ) — sinks 122.2 µA when pulled low, 403.3 µW in the resistor

$R_{\min }=\frac{V_{\mathrm{cc}}}{I_{\mathrm{sink}}}$ keeps the driver inside its sink rating, and $R_{\max }=\frac{V_{\mathrm{cc}}-V_{\mathrm{IH}}}{I_{\mathrm{leak}}}$ keeps the released line above the input threshold.

I²C bus

Example Use 1.8 kΩ on both lines (valid range 966.7 Ω to 3.541 kΩ) — sinks 1.611 mA per line at 3.3 V

Bounded below by the 3 mA a compliant device must sink at $V_{\mathrm{OL}}=0.4$ V, and above by the bus rise time: $R_{\max }=\frac{t_r}{0.8473\times C_b}$.