Full width row – 80% on wide screens (only)

I have a special heading & a text block contained in a 1/1 row.
I’d like to constrain the width of this row to, say 80% on wide screens, but retain 100% width on smaller screens, tablets, phone etc.
I was going to add a custom class to this row & target that using media queries – but I thought I’d better check with you guys first to make sure there wasn’t a better/easier way.
Obviously changing the inner padding settings to 0px 20% 0px 20% isn’t the way to go, as that carries across all screens sizes from what I can see – would that be correct?