I2C Pull-up Resistor Value Calculator

This calculator determines the safe operating window for your pull-up resistors based on the NXP I2C-bus specification. It ensures your signal rises fast enough to meet timing requirements while preventing your devices from drawing too much current when pulling the bus low.

Use this tool to:

  • Calculate Maximum Resistance (R_max): Ensures the signal reaches the logic “high” threshold within the required rise time (t_r) for your bus speed.
  • Calculate Minimum Resistance (R_min): Protects your ICs by ensuring they do not exceed their rated low-level sink current (I_OL).
  • Verify Bus Capacitance: Instantly see if your total bus capacitance is too high for your desired speed.
Bus Parameters
Calculated Range
Standard: Most ICs support 3mA sink current. Use 20mA only if your specific datasheet confirms Fast-mode Plus compatibility.

Expand your toolbox

Simplify hardware and firmware development using the Quickboards Library. Eliminate R&D uncertainty and cut design time by assembling subcircuit schematics from a library of Processors, Sensors, Power Management, ADC/DACs, Memory, Interface circuits and more. Download the full library here. 

Quickboards Schematic Library Collection

Tools, Converters & Calculators

Analog Filters

Power Management

PCB & Circuit Design 

Value Conversion Calculators