Apparatus for area measurement of elongated strips of different widths is described, which strips may be film to be treated, the strip to be measured preferably being initially delivered between driven rolls carried on parallel shafts, the strip passing over a driven roll having grooves at predetermined intervals, small freely rotatable rolls with peripheral projections such as rings thereon being provided which depress the strip into the grooves, the freely rotatable rolls being driven by engagement with the strip, the small rolls engaging actuation rolls having magnets carried therein to activate switches to generate pulses for counting by a counter to give an area indication and for other purposes, or the small rolls directly moving magnets for switch activation. The actuation rolls are preferably counterbalanced to reduce undesired unbalance.