How to calculate RPM from a square wave signal Voltage-Time graph
Hook up a voltmeter to the sensor.
Turn the wheel by hand one full revolution while counting the number of positive-going pulses generated. Call that n.
Measure the periodic time of the squarewave from your graph. Call that t. (It's 10 ms in the graph in your question.)


$$ RPM = 60 \times rps = 60 \frac 1 t \frac 1 n $$
where rps = revolutions per second.

$$ RPM = \frac {60}{tn} $$