Monthly budget calculator
Enter your income, fixed outgoings and variable spending to see exactly what you have left at the end of each month. See how your budget compares to the 50/30/20 rule and get personalised tips based on your numbers.
The single most effective budgeting move is to set up a standing order that moves your savings to a separate account on the day your salary arrives. If the money is gone before you see it, you cannot spend it. Peter did not budget obsessively — he just made sure the important things happened automatically and lived on what was left.
Please note: This calculator is for personal budgeting guidance only. All figures are estimates based on the inputs you provide. The 50/30/20 rule is a general guideline and may not suit every financial situation. This is not financial advice. For help with debt or financial difficulty, free support is available from charities such as StepChange and Citizens Advice.
What is a monthly budget calculator?
A monthly budget calculator helps you map your income against your outgoings to show how much is left at the end of each month – and where it is going. It structures spending into categories (housing, transport, food, subscriptions, savings) to give a clear picture of the budget rather than a vague sense that money disappears between paydays.
The goal is not to restrict spending but to make spending deliberate. A budget that is never reviewed is a plan that has already been abandoned – the value of this calculator is in the annual or quarterly review, not in creating a perfect first draft.
How to use this calculator
Monthly income: Enter your total monthly take-home pay – the net amount that lands in your bank account, not your gross salary. If you have multiple income sources (salary, rental income, freelance), include all regular monthly income.
Fixed expenses: Costs that are the same each month – rent or mortgage payment, insurance premiums, subscriptions, loan repayments, and council tax. These are non-negotiable in the short term.
Variable expenses: Costs that change month to month – groceries, eating out, entertainment, clothing, transport. Enter realistic averages based on actual spending, not aspirational targets.
Savings: Enter your current regular savings – pension contributions (if not already deducted from take-home), ISA standing order, emergency fund contribution. If these are currently zero, the calculator shows how much is available to direct toward them.
Reading the result: The calculator shows your monthly surplus or deficit. A surplus means money is available for savings or discretionary spending. A deficit means outgoings exceed income, which requires either reducing expenses or increasing income.
Frequently asked questions
What is a good savings rate? A commonly cited target is to save at least 20% of take-home pay, divided among a pension, an ISA, and an emergency fund. However, the right rate depends on your age, existing savings, and financial goals. Even a 5-10% savings rate is meaningfully better than zero.
How do I handle irregular expenses in a budget? Annual or irregular costs (car insurance, home maintenance, Christmas, holidays) should be divided by 12 and treated as monthly amounts. This creates a notional monthly allocation that accumulates in a separate account and is available when the cost is incurred – converting irregular, large costs into predictable monthly ones.
What if my budget shows a deficit? A deficit means spending exceeds income. The options are to reduce expenses (reviewing subscriptions, renegotiating bills, reducing discretionary spending) or to increase income (a pay rise, additional work, selling assets). The calculator identifies which categories are largest and therefore where changes have the most impact.
The information on this site is for educational and informational purposes only. Nothing on Be More Peter constitutes financial advice, and nothing should be treated as such. The calculators, articles and tools on this site are designed to help you understand financial concepts and run indicative numbers - they are not a substitute for professional advice tailored to your specific circumstances. Before making any financial decision - including decisions about mortgages, pensions, investments, savings or insurance — you should seek independent financial advice from a qualified adviser who is authorised and regulated by the Financial Conduct Authority (FCA). Calculator results are estimates based on the information you enter and the assumptions built into the tool. They are illustrative only and should not be relied upon as accurate projections. Rates, thresholds and rules change regularly - always verify figures with an appropriate professional or official source before acting on them. Be More Peter is not authorised or regulated by the FCA. The content on this site does not constitute a financial promotion.
Related tools and posts
- Take-home pay calculator — confirm your monthly starting point
- Compound interest calculator — what savings surplus produces over time
- Emergency fund post — first use of any surplus
- New Year money reset — the one-hour financial audit