Maths calculators

Percentage calculator

No shame here. Percentages trip everyone up. Pick the type of calculation you need below and get your answer instantly with a plain-English explanation of how it works.

What do you need to work out?

Percentage

Of this number

Answer

20% of 350 is 70

How it works: divide the percentage by 100, then multiply by the number. So 20 / 100 = 0.2, then 0.2 x 350 = 70.

This number

As a percentage of

Answer

20%

70 is 20% of 350

How it works: divide the part by the total, then multiply by 100. So 70 / 350 = 0.2, then 0.2 x 100 = 20%.

Original value

New value

Percentage increase

25%

200 increased to 250 is a 25% rise

How it works: subtract the original from the new value, divide by the original, then multiply by 100. So (250 - 200) / 200 x 100 = 25%.

Starting number

Percentage to add or remove

Add or remove?

After adding 20%

600

500 plus 20% = 600

How it works: multiply the number by (1 + percentage / 100). So 500 x 1.20 = 600.

Real-world examples - click any to load it

Mortgage deposit

5% of £250,000

= £12,500

Deposit percentage

£60,000 of £300,000

= 20% deposit

Income tax (basic rate)

20% of £45,000

= £9,000

House price growth

£180,000 to £220,000

= 22.2% increase

Sale discount

Remove 5% from £250

= £237.50

Stamp duty (2% band)

2% of £200,000

= £4,000

Peter's tip

Percentages show up everywhere in personal finance - interest rates, tax bands, mortgage deposits, investment returns, stamp duty bands. The one mental trick worth knowing: to find any percentage of a number, just move the decimal point two places left. 5% of 200 is the same as 0.05 x 200 = 10. Once that clicks, most percentage questions become much easier.

Percentages in mortgages

Your LTV, your interest rate, stamp duty bands, and deposit size are all expressed as percentages. Understanding how they interact helps you make better decisions.

Percentage vs percentage points

If your interest rate rises from 4% to 5%, that is a 1 percentage point increase - but it is a 25% increase in the rate itself. These are very different things.

Compound vs simple

Simple interest applies a percentage to the original amount only. Compound interest applies it to the growing total. This is why savings and debts both grow faster than you expect.

The reverse percentage trap

Adding 20% then removing 20% does not get you back to the start. Adding 20% to 100 gives 120. Removing 20% of 120 gives 96. This trips up a lot of people.

Please note: This calculator is for general mathematical guidance only. Results are rounded to two decimal places where appropriate. For financial decisions involving percentages, always verify figures with a qualified adviser.

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.

What does the percentage calculator do?

The percentage calculator covers the three calculations that come up most in everyday financial life:

Find a percentage of a number – what is 20% of £450? (£90)
What percentage is one number of another? – £90 is what percentage of £450? (20%)
Percentage increase or decrease – if a price rises from £450 to £540, what is the percentage increase? (20%)

All three are simple once you know the method, but easy to muddle under pressure. The calculator handles the arithmetic instantly, so you can focus on what the number means.

Why percentages matter in financial life

Percentages appear constantly in financial contexts – interest rates, tax rates, commission rates, investment returns, price changes, salary increases, mortgage LTV, deposit percentages, discount calculations. Being confident with percentages means being able to check figures rather than accepting them, compare rates accurately, and understand what a percentage change actually means in pounds.

Frequently asked questions

How do I calculate VAT? To find the VAT-inclusive price (adding 20% VAT): multiply the net price by 1.20. To find the VAT amount on a VAT-inclusive price: divide the total price by 6. To remove VAT from a VAT-inclusive price: divide by 1.20.

What is the difference between percentage points and percentage change? If an interest rate rises from 3% to 5%, it has risen by 2 percentage points — but by 67% as a percentage change ((5−3)÷3 × 100). These two measures are often confused in financial news – “interest rates rose by 2%” might mean 2 percentage points (from 3% to 5%) or 2% of the current rate (from 5% to 5.1%).

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.