I2C Pull-up Resistor Calculator

Calculate valid pull-up resistor range for SDA/SCL using sink current and rise-time constraints.

Calculator

Bus voltage VCC (V) VOL max (V) Sink current IOL (mA) Total bus capacitance (pF) I2C mode

Rise-time limit—

Rmin (sink current)—

Rmax (rise time)—

Suggested target—

Nearest E24—

Estimated rise time—

Enter I2C bus values.

Electrical limit: Rmin = (VCC - VOLmax) / IOL. Timing limit: Rmax = tr / (0.8473 × Cbus). Choose resistor between Rmin and Rmax.

Pull-up too weak makes edges too slow and may violate rise-time specs.

Too-low value increases sink current and may exceed device IOL capability.