The big advantage of cash envelopes is that, if you budget properly, you will always have the cash to pay a bill when it comes due. No more worrying about where the money will come from, be it for mortgage or rent, utilities, car payments, repairs, taxes, discretionary spending, etc.
Include all variable expenses now, car maintenance, electricity, heating, these can vary throughout the year you need to calculate them and come up with an average monthly amount. None essential expenses like eating out coffee at Starbucks, weekend getaways, extravagant vacations, fancy clothing, motorcycles, ATV's, if you use them, write them down, realize these are wants, not needs. Now total these all up, fixed expenses, variable expenses, and non_essential expenses,there you now have your total expenses.