# How to convert Sars-CoV-2 ORF1ab codon positions to ORF1b positions?

Some websites mention amino acid mutations as ORF1ab, most however use ORF1a/b instead.

So how can I translate from one to the other? What do I need to subtract from say ORF1ab:4588I to get the corresponding N in ORF1b:<N>I?

ORF1ab:4588I corresponds to ORF1b:187I so one needs to subtract 4401 to go from 1ab to 1b and add 4401 to go the other way.