A more rational approach is to take the weight of one square metre or paper and use this as the basis of substance. In practice it may be preferable to weigh, say, a ream of paper and divide this by 500 to give more precise figure. This will give a consistent pH value, such as 80 grammes per square metre, contracted to 80 g/m², which will remain constant regardless of sheet size, caliper or ream weight.