The 50/30/20 rule: how to build a household budget

What is the 50/30/20 rule?

The 50/30/20 rule is a simple way to organise the money that comes in each month¹. Instead of tracking dozens of spending categories, it groups everything into just three:

50% needs · 30% wants · 20% savings and debt

The idea was popularised by US senator Elizabeth Warren in the book All Your Worth. Its strength is its simplicity: it gives a clear target for every euro and makes it easy to see, at a glance, whether your budget is balanced.

The three slices

50% for needs. These are the essentials you genuinely have to pay: rent or mortgage, food, transport, water, electricity, gas and phone bills, insurance and minimum loan payments. If they disappeared, your day-to-day life would be at risk.

30% for wants. This is everything optional that improves your quality of life: dining out, leisure, streaming subscriptions, the gym, travel and non-essential purchases. It is the easiest slice to adjust when you need to save.

20% for savings and debt. This includes saving, investing and paying off loans beyond the minimum. It is the part that builds your future: the emergency fund, retirement savings and the path to financial independence.

You do not need to do the maths by hand. Our household budget calculator splits your income across the three slices and lets you compare it with what you spend today.

It applies to net income

A common mistake is to apply the rule to gross salary. The percentages are calculated on net income, that is, what lands in your account after income tax and Social Security are deducted. If you do not know your net pay, work it out first with the net salary calculator and use that figure as your starting point.

For example, on €2,000 net a month, the rule gives:

• €1,000 for needs (50%);
• €600 for wants (30%);
• €400 for savings and debt (20%).

How to adapt the rule to your life

The 50/30/20 rule is a starting point, not a rigid law. In Portugal, especially in Lisbon and Porto, housing alone can consume more than half of your income. If your needs already exceed 50%, do not abandon the rule: use it as a target to reach over time.

Some ways to balance the budget when one slice overflows:

• Temporarily cut wants (the 30% slice) to free up room.
• Raise your income, through training, changing jobs or a side income.
• Find cheaper housing or share costs, where possible.
• Renegotiate loans to lower the monthly payment within needs.

If you have more ambitious goals, you can flip the logic and save more than 20% (for example, 50% of your income, as followers of the FIRE movement do) by cutting back on wants.

How to start in three steps

1. Work out your monthly net income. It is the basis of the whole calculation.
2. List your spending over recent months and group it into needs, wants and savings. Bank statements and your banking app help.
3. Compare it with the 50/30/20 rule and adjust whichever slice is most out of line, starting with wants.

Try your own numbers in the household budget calculator: enter your income and what you spend today, and see, slice by slice, what you can adjust to save more each month.