Work out i2c bus capacitance limit instantly with clear inputs, formula shown and shareable results.
I2C is limited to 400 pF of bus capacitance because rise time is 0.8473 x R x C for the RC pull-up. Fast mode allows 300 ns of rise time, so the pull-up resistor and total capacitance together decide the maximum usable speed.
I2C rise time
tr = 0.8473 x Rpullup x Cbus; the specification limits Cbus to 400 pF
To a point. Lower resistance speeds the rise but raises the sink current, and the specification limits low-level output current to 3 mA, which sets a minimum resistance.
Use an I2C buffer or bus extender, split the bus into segments, or switch to a multi-master-capable protocol designed for longer runs.