Plan each paycheck before it lands: bills due before the next payday, groceries, gas, savings and what is left to spend.
Write what you plan to spend in the first column and what you actually spent in the second; the difference and the totals work themselves out.
The file works in Excel, Numbers, Google Sheets and LibreOffice. If you would rather have it done for you, Xpenses reminds you of every bill and works out how much you will have at the end of each month.