Oxidizer mass ratio is the mass of oxidizer divided by the total mass of fuel, oxidizer and propellant. The oxidizer mass ratio is low if the oxidizer is high in oxygen, which has two oxidizing electrons and a molecular weight of sixteen. The oxidizer mass ratio is higher if the oxidizer is high in hydrogen, which has one reducing electron and a molecular weight of one. So diatomic oxygen gives a low fuel mass ratio and hydrogen peroxide gives a higher fuel mass ratio.

A typical oxidizer mass ratio is three quarters. This is why there have been many attempts to power high speed craft with atmospheric oxygen. However, this is not practical above about mach three because the equipment needed to use dilute, gaseous oxygen at that speed weighs more than an onboard liquid oxidizer. In general for orbital craft, it is useful to have a first stage operating up to about mach three to use atmospheric oxygen and the second stage to use rockets. Given the combustion efficiency, fuel molecular, fuel molar, mixture, mixture oxidizer mix, oxidizer mix molecular and oxidizer propellant mix the oxidizer mass ratio can be calculated.

fuel molar ratio = 1.0 - mixture
mixture oxidizer mix = 1.0 + mixture

unreacted fuel = 0.0
if ( fuel molar ratio > mixture oxidizer mix ) {
    unreacted fuel = fuel molar ratio - mixture oxidizer mix
}

If the combustion isn't ideal:

if ( combustion efficiency < 1.0 ) {

Then the quadratic equation is used to determine the part of each reactant that combines chemically:

    ratio = 9999999.9
    if ( fuel molar ratio != 0.0 ) {
    ratio = mixture oxidizer mix / fuel molar ratio
    }
    unreactability = 1.0 / ( 1.0 - combustion efficiency )
    a = 2 * unreactability * unreactability
    b = a * ( ratio - 1.0 )
    c = ratio + 1.0
    unreacted = 0.5 / a * ( sqrt( b * b + 4.0 * a * c ) - b )
    unreacted fuel = fuel molar ratio * unreacted
}

fuel molar ratio *= fuel molar
mixture oxidizer mix *= oxidizer mix molar
mixture molar = fuel molar ratio + mixture oxidizer mix
mixture oxidizer mix /= mixture molar

fuel mass ratio = fuel molar ratio * fuel molecular
oxidizer mix mass ratio = mixture oxidizer mix * oxidizer mix molecular
mixture mass = fuel mass ratio + oxidizer mix mass ratio
oxidizer mix mass ratio /= mixture mass
oxidizer mass ratio = oxidizer propellant mix * oxidizer mix mass ratio
 
 

This is used in bipropellant rocket, tripropellant rocket, pumped rocket and rocket cost.
 
  Rocket