DPO or days before period due?

Angie🌈🙏🏻✨
Just a question regarding which one is best to calculate by when testing early? Days post ovulation or days until period is due? I think I ovulated on Day 16 of my cycle - which means 9-12 DPO is right before my period is due as I have a 26 day cycle... I tested this morning because I couldn't wait - period due in 5 days and was very clearly negative...