This depends on the requirements of the engine manufacturer. Once
you know the ratio, it's a mathematical calculation. For example, for a
50:1 ratio, for 1 Gallon of Gas. There is 128 ounces in a gallon
divided by 50, comes to 2.56 ounces, rounded to the nearest tenth of an
ounce is 2.6.

We also found this handy calculator on line: Gas Ratio Oil Mixture Ratio Calculator