A budget is not there to forbid you things. It is there to decide in advance where every euro you earn will go. With one hour a month you can find out how much you really spend, how much you can save and where your money leaks away.
This guide shows how to build a monthly budget step by step and how to adapt the 50/30/20 rule, one of the simplest ways to split your income. The examples use euros, but the method works in any currency.
What is the 50/30/20 rule?
The rule splits your take-home pay into three buckets: 50% for needs, 30% for wants and 20% for saving, investing or paying down debt. It was popularised by US senator Elizabeth Warren and her daughter Amelia Warren Tyagi in their 2005 book All Your Worth. Treat it as a starting point, not a law.
Step 1: work out your net income
Write down what you actually receive each month, after tax and social security contributions have been deducted: net salary, occasional income, pensions or benefits. If your income varies, use the average of the last six to twelve months or, to be safe, the lowest month of the year.
Step 2: find out where your money goes
Download one to three months of bank transactions and sort them into categories. You do not need an app: a spreadsheet or a sheet of paper is enough. The goal is to see the real picture, not the one you think you have.
Step 3: separate fixed costs, variable costs and savings
- Fixed costs: rent or mortgage, utilities, insurance, loan repayments, transport and phone.
- Necessary variable costs: groceries, pharmacy, fuel, basic clothing.
- Optional variable costs: leisure, restaurants, subscriptions and unplanned purchases.
- Saving and investing: what you set aside each month, including your emergency fund.
Step 4: split your income with the 50/30/20 rule
- 50% for needs: housing, utilities, basic food, transport, insurance and debt repayments.
- 30% for wants: leisure, travel, restaurants, treats.
- 20% for saving and investing, or for paying off debt faster.
With a net income of 1,800 euros a month, it would look like this:
| Bucket | Share | Amount per month |
|---|---|---|
| Needs | 50% | €900 |
| Wants | 30% | €540 |
| Saving and investing | 20% | €360 |
Here is one way those amounts could be spent. The figures are illustrative:
| Bucket | Item | Amount |
|---|---|---|
| Needs | Rent or mortgage | €520 |
| Needs | Utilities and phone | €110 |
| Needs | Groceries | €200 |
| Needs | Transport | €70 |
| Wants | Eating out | €150 |
| Wants | Leisure and hobbies | €120 |
| Wants | Subscriptions | €40 |
| Wants | Shopping | €130 |
| Wants | Travel fund | €100 |
| Saving | Emergency fund | €200 |
| Saving | Long-term investing | €160 |
How to adapt it to your situation
The rule is a guide. If you live in a city with high rents, your needs may exceed 50%: in that case try 60/20/20 or 60/25/15. What matters is to always keep a share for saving, even if it is small at first, and to raise it as your income improves or your fixed costs fall.
Pay your future self first
The trick that works best is automation: set up a transfer to your savings account on the day you get paid. What you do not see in your current account, you do not spend. Once the saving is done, spend what is left without guilt.
Common mistakes
- Forgetting annual expenses. Car insurance, property tax or holidays are not paid every month, but you need to provision for them: add them up and divide by 12.
- Making the budget too rigid. If you leave no room for fun, you will drop the budget within two weeks.
- Never reviewing it. Spend a few minutes each month comparing plan and reality, and adjust.
- Saving only what is left over. If saving depends on what remains at the end of the month, it will almost always be zero.
Frequently asked questions
Is the 50/30/20 rule realistic on a low income?
It can be tight. If necessities take 60% or 70% of your income, start with whatever you can save, even 5%, and build the habit first. You can raise the percentage later.
Where do debt repayments go?
The minimum payments you must make belong in needs. Extra payments to clear a debt faster can come out of the 20% bucket.
How often should I review my budget?
Once a month is enough. Compare what you planned with what you spent, move a few amounts and carry on.
Next step
Once your spending is under control, the first thing to build is an emergency fund. After that, if you want your savings to grow, find out how compound interest works and try our compound interest calculator.
This article is for information and education only. It is not personalised financial, tax or legal advice: for an important decision, consult a qualified professional. Last reviewed: October 2026.