It is neither! 35mm is the overall width of the film. And, there are many different standards for frame sizes; the same film stock is used for still photography and motion picture photography, both are different. But, a typical 35mm frame is 16mm tall.
The space between the sprocket holes is 25.375mm, or very, very slightly under 1 inch.
Is 35mm both the width and the height of a frame? If so we can then easily use frame as units to convert between metric and imperial.
It is neither! 35mm is the overall width of the film. And, there are many different standards for frame sizes; the same film stock is used for still photography and motion picture photography, both are different. But, a typical 35mm frame is 16mm tall.
The space between the sprocket holes is 25.375mm, or very, very slightly under 1 inch.