Percentage Calculator Guide & Help

Quick Start & Requirements

JavaScript Required
Just Percent runs entirely in your browser. Just make sure JavaScript is enabled to get started.
Decimal Separators
Use the decimal separator that matches your locale settings. For example:
- In the US and UK, use a dot (.), e.g., 10.5.
- In many European countries, use a comma (,), e.g., 10,5.
Thousands Separator
Thousands separators are ignored when you type. You don't need to include them. The app uses your locale settings to interpret pasted numbers correctly. For example, "1,000" is read as one thousand in US locale (where comma is the thousands separator) but as one in German locale (where comma is the decimal separator). Similarly, "1.000" is read as one thousand in German locale but as one in US locale.
Instant Results
Calculations happen in real-time as you type. No need to hunt for a "Calculate" button.

Helpful Calculator Features

Our calculators include several features to make your calculations faster and easier:

Smart Clipboard

Paste numbers instantly with the Paste button (Chrome only, after allowing clipboard access when prompted).
Click Save calculation to copy the result to your clipboard and save it to your list.
Results are copied as plain numbers (no currency symbols, percent signs, or formatting), so they paste cleanly into any app.

Keyboard Shortcuts

Enter moves to the next field, or when pressed in the last field, saves to list, copies the result to clipboard, and returns focus to the first field.
Escape clears everything for a fresh start.
Space jumps between fields.

Drag-to-Adjust Values

Click and hold any number field, then drag left or right to adjust the value.
Power user tip! Hold Alt (or Option) for larger jumps, or Shift for whole numbers.

Saved Calculations

The current calculation is saved when you press Enter in the last field or click the Save calculation button.
Clicking any previous entry reloads it instantly.
Single items can be cleared, or you can wipe the slate clean with one click.
Your data stays private - everything is stored right in your browser.
We keep your last 20 calculations, automatically making room for new ones.

Customize Your Layout

Drag and drop calculator cards to rearrange them.
Put your favorites at the top for quick access.
Your layout is saved automatically.

Collapse Calculator Sections

Hover over the top edge of any calculator card to reveal chevron controls (↑ ↓).
Use the chevrons to progressively hide or show sections like saved list, hints, or the input form.
The system automatically skips levels that have no effect in your current view.
Your visibility preferences are saved per calculator and restored on your next visit.
On touch devices, the chevron controls are always visible.

Mobile-Friendly

Works perfectly on phones, tablets, and desktops.
Touch-friendly buttons and clear navigation.

Extras

One-click Dark Mode.
Visual formulas to help you understand the maths.
Smart validation ensuring precise results every time.

Basic Percentage CALCULATOR

Calculate the percentage value of a given number.

Practical Uses

Daily Nutritional Value:
40% [X] of a standard UK 2,000 [Y] calorie diet is how many calories [Z]?
800 calories

Exam Marks:
Scoring 85% [X] on a 120 [Y] mark University exam earns how many marks [Z]?
102 marks
Investment Interest:
5% [X] APR on a £1,000 [Y] high-yield ISA earns how much [Z]?
£50
Restaurant Tip:
A 15% [X] tip on a £60 [Y] restaurant bill comes to how much [Z]?
£9
Sale Discount:
20% [X] off a £80 [Y] pair of designer jeans saves you how much [Z]?
£16
VAT Calculation:
20% [X] VAT on a £250 [Y] laptop comes to how much [Z]?
£50

How to Use

Enter the percentage in the first box.
Enter the total number in the second box.
The result appears instantly in the third box.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Basic Percentage calculator uses this formula:

\text{Result} = \frac{\text{Percentage}}{100} \times \text{Number}

Example: What is 20% of 80?

\frac{20}{100} \times 80 = 16

So 20% of 80 is 16.

Go to Basic Percentage CALCULATOR

Original Value CALCULATOR

The Original Value calculator (also known as reverse percentage calculator) helps you find the original value when you know a percentage and its result. This is useful for working backward from a known percentage to find the original amount.

Practical Uses

Pre-Discount Price:
25% [X] of what original price [Y] is a £50 [Z] discount on a smartwatch?
£200
Pre-VAT Amount:
20% [X] of what pre-VAT amount [Y] is £40 [Z] VAT?
£200
Original Value:
15% [X] of what dinner bill [Y] is a £30 [Z] tip?
£200
Pre-Rise Salary:
10% [X] of what original base salary [Y] is a £4,000 [Z] pay rise?
£40,000
Investment Principal:
12% [X] of what original ISA balance [Y] is a £2,400 [Z] return?
£20,000
Total Budget:
30% [X] of what total Christmas budget [Y] is £600 [Z]?
£2,000

How to Use

Enter the percentage in the first box.
Enter the part value in the third box.
The original value appears instantly in the middle box.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Original Value calculator uses this formula:

\text{Original Value} = \frac{\text{Result} \times 100\%}{\text{Percentage}}

Example: If 15% equals 30, the original value is:

\frac{16 \times 100\%}{20} = 80

So the original value is 200.

Important Note

When the percentage is 0%, the calculation is undefined because you cannot divide by zero.

Go to Original Value CALCULATOR

Part-to-Whole Percentage CALCULATOR

Find what percentage one number is of another.

Practical Uses

Goal Conversion Rate:
What is the conversion rate [X%] for a Premier League striker with 100 [Y] shots and 30 [Z] goals?
30%
Rent Share:
What percentage [X%] of your £3,000 [Y] monthly income goes to £900 [Z] rent in Manchester?
30%
Market Share:
What is a company's market share [X%] if total EV sales are £1,000,000 [Y] and one company sells £250,000 [Z]?
25%
Savings Progress:
What percentage [X%] of your £10,000 [Y] emergency fund have you reached with £7,500 [Z] saved?
75%
Task Completion:
What percentage [X%] of 24 [Y] weekly chores is 18 [Z] completed tasks?
75%
Exam Score:
What is your mark [X%] on a 100 [Y] mark A-Level exam when scoring 85 [Z] marks?
85%

How to Use

Enter the whole value in the middle box.
Enter the part value in the third box.
The percentage result appears instantly in the first box.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Part-to-Whole Percentage calculator uses this formula:

\text{Percentage} = \frac{\text{Z}}{\text{Y}} \times 100\%

For example, to find what percentage 25 is of 100, the calculator computes:

\frac{25}{100} \times 100\% = 25\%

So 25 is 25% of 100.

Important Note

When the whole/total value is 0, the percentage is undefined because you cannot divide by zero.

Go to Part-to-Whole Percentage CALCULATOR

Percentage Change CALCULATOR

Calculate the percentage difference between two values to determine increases or decreases.

Practical Uses

Inflation Rate:
A concert ticket rising from £80 [Original] to £82.40 [New] represents what inflation rate [Change%]?
3%
Performance Improvement:
Monthly sales leads improving from 70 [Original] to 84 [New] represents what percentage improvement [Change%]?
20%
Revenue Growth:
Small business revenue growing from £800,000 [Original] to £960,000 [New] represents what percentage growth [Change%]?
20%
Salary Change:
A store manager's salary increase from £40,000 [Original] to £43,200 [New] represents what percentage pay rise [Change%]?
8%
Share Price Change:
BP shares going from £40 [Original] to £60 [New] represents what percentage change [Change%]?
50% increase
Website Traffic Change:
A drop in Etsy shop visits from 10,000 [Original] to 8,500 [New] represents what percentage change [Change%]?
15% decrease
Weight Loss:
Weight dropping from 82 [Original] kg to 74 [New] kg on a healthy diet represents what percentage change [Change%]?
10% decrease

How to Use

Enter the original value in the first box.
Enter the new value in the second box.
The percentage change appears instantly.
A negative result means the value decreased.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Percentage Change calculator uses this formula:

\text{Change}\% = \frac{\text{New} - \text{Old}}{\text{Old}} \times 100

Example: What is the percentage change from 50 to 75?

\frac{75 - 50}{50} \times 100 = 50\%

The value increased by 50%.

Go to Percentage Change CALCULATOR

Increased Value CALCULATOR

See what you get after boosting a value by the Increase %.

Practical Uses

Budget Boost:
A £4,000 [Original] holiday budget increased by 25% [Increase] becomes what [New]?
£5,000
Investment Growth:
A £2,000 [Original] Stocks & Shares ISA growing by 12% [Increase] becomes what [New]?
£2,240
Population Growth:
A city like Reading of 100,000 [Original] people with 3% [Increase] growth reaches what population [New]?
103,000
Price Inflation:
A £100 [Original] weekly shop with 5% [Increase] inflation becomes what [New]?
£105
Rent Increase:
Monthly rent of £1,000 [Original] in Manchester with a 7% [Increase] hike becomes what [New]?
£1,070
Salary Increase:
A £35,000 [Original] nurse salary increased by 8% [Increase] becomes what [New]?
£37,800

How to Use

Enter the original value in the first box.
Enter the increase percentage in the second box.
The new value (after increase) appears instantly.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Increased Value calculator uses this formula:

\text{New Value} = \text{Original} \times (1 + \frac{\text{Increase}\%}{100})

Example: What is 100 increased by 25%?

100 \times (1 + \frac{25}{100}) = 125

100 plus 25% equals 125.

Go to Increased Value CALCULATOR

Original Before Increase CALCULATOR

Calculate the original value before a percentage increase, given the new value and percentage increase.

Practical Uses

Budget (Pre-Increase):
What was the original wedding budget [Original] before a 25% [Increase] boost made it £6,250 [New]?
£5,000
Investment (Pre-Growth):
What was the original ISA investment [Original] before a 12% [Increase] growth made it worth £2,240 [New]?
£2,000
Price Before Hike:
What was the original TV subscription [Original] before a 5% [Increase] hike made it £126 [New]?
£120
Rent Before Rise:
What was the original rent [Original] in Leeds before a 7% [Increase] rise made it £1,070 [New]?
£1,000
Pre-Growth Population:
What was the original population of Swindon [Original] before a 3% [Increase] growth brought it to 103,000 [New] people?
100,000
Salary Before Rise:
What was the original start-up salary [Original] before an 8% [Increase] pay rise made it £43,200 [New]?
£40,000

How to Use

Enter the new value (after the increase) in the first box.
Enter the increase percentage in the second box.
The original value (before increase) appears instantly.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Original Before Increase calculator uses this formula:

\text{Original} = \frac{\text{New Value}}{1 + \frac{\text{Increase}\%}{100}}

Example: What was the original if 125 is after a 25% increase?

\frac{125}{1 + \frac{25}{100}} = 100

The original value was 100.

Go to Original Before Increase CALCULATOR

Decreased Value CALCULATOR

Calculate the new value after decreasing an original amount by a specific percentage.

Practical Uses

Budget Cut:
A £8,000 [Original] wedding budget cut by 25% [Decrease] becomes what [New]?
£6,000
Employee Reduction:
A 500 [Original]-person tech startup reduced by 10% [Decrease] leaves how many people [New]?
450 people
Energy Savings:
A £150 [Original] summer energy bill reduced by 18% [Decrease] becomes what [New]?
£123
Sale Discount:
A £250 [Original] winter jacket with a 30% [Decrease] discount costs what [New]?
£175
Share Price Drop:
A £40 [Original] energy share declining by 12% [Decrease] becomes what [New]?
£35.20
Weight Loss:
Weighing 82 [Original] kg and losing 15% [Decrease] for summer leaves what weight [New]?
70 kg

How to Use

Enter the original value in the first box.
Enter the decrease percentage in the second box.
The new value (after decrease) appears instantly.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Decreased Value calculator uses this formula:

\text{New Value} = \text{Original Value} \times (1 - \frac{\text{Decrease}}{100})

Example: What is 100 decreased by 25%?

2000 \times (1 - \frac{15}{100}) = 1700

100 minus 25% equals 75.

Go to Decreased Value CALCULATOR

Original Before Decrease CALCULATOR

Calculate the original value before a percentage decrease, given the new value and percentage decrease.

Practical Uses

Budget (Pre-Cut):
What was the original renovation budget [Original] before a 25% [Decrease] cut made it £3,750 [New]?
£5,000
Investment (Pre-Loss):
What was the original share portfolio [Original] before a 12% [Decrease] loss made it worth £1,760 [New]?
£2,000
Expense Before Cut:
What were the original subscription costs [Original] before a 7% [Decrease] cut made them £930 [New]?
£1,000
Salary Before Cut:
What was the original freelance income [Original] before an 8% [Decrease] drop made it £38,640 [New]?
£42,000
Pre-Decline Population:
What was the original population of Liverpool [Original] before a 3% [Decrease] decline left it at 97,000 [New] people?
100,000
Price Before Discount:
What was the original price [Original] before a 5% [Decrease] loyalty card discount made it £95 [New]?
£100

How to Use

Enter the new value (after the decrease) in the first box.
Enter the decrease percentage in the second box.
The original value (before decrease) appears instantly.
Check "Round" if you want to keep the result to two decimal places.
Save it to your list with Enter or the "Save calculation" button.

How It Works

The Original Before Decrease calculator uses this formula:

\text{Original} = \frac{\text{New Value}}{1 - \frac{\text{Decrease}\%}{100}}

Example: What was the original if 75 is after a 25% decrease?

\frac{75}{1 - \frac{25}{100}} = 100

The original value was 100.

Go to Original Before Decrease CALCULATOR