PVC pipe sizes - what the ???

I bought some Schedule 40 PVC and fittings at Home Depot. They're all labelled as 1/2" ASTM D1785, but it's larger than expected. I took its measurements with a caliper, and get an OD of over 1", ID about 0.84... From all the charts I can find this appears to match the specs for 3/4" nominal. Am I missing something here? :confused: