Early on in my training I saw numbers between 60% and 70% of your bodyweight called the bench press equivalent poundage of a pushup.
Most sources said either ⅔ or 65% bw.
I call that difference negligible, and use them when I calculate the bench equivalent of my weighted pushups.
The Equation :
bw x .66 + x
x is the number of pounds on the upper back, I just straight lump sum add it to the pushup equation since the resistence is centered at my scapula directly across from the chest, the prime mover.
Who says you need a barbell to get the training effect of heavy benching?
Persistence & Tenacity