How to Calculate a Percentage Increase With a Calculator

Calculating a percentage increase with a calculator is straightforward once you separate the size of the increase from the original amount. This guide explains the formula, the exact calculator keystrokes, useful shortcuts, common mistakes, and situations where the method needs extra care.

The percentage increase formula

Use this formula when a value changes from an original amount to a new, higher amount:

Percentage increase = ((New value − Original value) ÷ Original value) × 100

The original value is the starting number, and the new value is the number after the increase. The difference between them tells you how much the value increased. Dividing that difference by the original value shows the increase relative to the starting point. Multiplying by 100 converts the decimal into a percentage.

For example, if a monthly subscription rises from $40 to $50:

Increase = 50 − 40 = 10
Percentage increase = (10 ÷ 40) × 100 = 25%

The price increased by 25%, not 20%. The $10 increase is one-quarter of the original $40 price.

How to calculate it on a basic calculator

A basic calculator is enough. Follow these steps:

Write down the original value.
Write down the new value.
Subtract the original value from the new value.
Divide the result by the original value.
Multiply by 100.
Add the percent sign to the answer.

Suppose a product cost $75 and now costs $90:

90 − 75 = 15
15 ÷ 75 = 0.2
0.2 × 100 = 20

The percentage increase is 20%.

On many calculators, you can enter the entire expression like this:

(90 − 75) ÷ 75 × 100

If your calculator does not support parentheses, calculate the subtraction first, then continue with the result:

90 − 75 = 15
15 ÷ 75 = 0.2
0.2 × 100 = 20

The order matters. Always divide by the original value, not the new value.

A worked example with a salary increase

Imagine your annual salary changes from $48,000 to $52,800. To find the percentage increase:

New salary − Original salary = 52,800 − 48,000 = 4,800
4,800 ÷ 48,000 = 0.1
0.1 × 100 = 10%

The salary increased by 10%.

You can also use the increase amount directly if it is already known. If your salary increased by $4,800 from a starting salary of $48,000:

4,800 ÷ 48,000 × 100 = 10%

This is useful for pay raises, commission changes, rent adjustments, and annual budget comparisons.

Quick examples for everyday calculations

The same process works for almost any measurable quantity that starts above zero.

Original value	New value	Calculation	Percentage increase
$20	$25	$5 ÷ $20 × 100	25%
80 points	92 points	12 ÷ 80 × 100	15%
1,200 visitors	1,500 visitors	300 ÷ 1,200 × 100	25%
2.5 liters	3 liters	0.5 ÷ 2.5 × 100	20%
600 units	660 units	60 ÷ 600 × 100	10%

For the points example, the increase is 12 points. Dividing 12 by the original 80 gives 0.15, which becomes 15% after multiplying by 100.

The fastest calculator shortcut

If you know both the original and new values, you can calculate the new value as a percentage of the original first:

New value ÷ Original value × 100

Then subtract 100 from the result:

Percentage increase = (New value ÷ Original value × 100) − 100

For a price rising from $120 to $150:

150 ÷ 120 × 100 = 125%
125% − 100% = 25%

The new price is 125% of the original price, so the increase is 25%.

Some calculators allow this shorter form:

150 ÷ 120 − 1 = 0.25
0.25 × 100 = 25%

This method is especially convenient when comparing financial reports, website traffic, inventory totals, or measurements in a spreadsheet-like workflow.

Using a calculator’s percent key

Calculator percent keys do not all behave identically. On many basic calculators, you can enter an expression such as:

75 + 20%

and receive 90, because the calculator interprets 20% as 20% of 75. This is useful when you already know the percentage increase and want to calculate the new total.

However, percent keys can be confusing when you are trying to discover the percentage increase. The most reliable approach is to use the explicit formula:

(New value − Original value) ÷ Original value × 100

If you use a phone calculator or scientific calculator, entering the full formula with parentheses usually gives the clearest result. Do not assume that pressing the percent key will produce the same result on every device.

Finding the new value after a known percentage increase

Sometimes you are given the percentage increase and need to calculate the new amount. Use this formula:

New value = Original value × (1 + Percentage increase ÷ 100)

For example, to increase $240 by 15%:

240 × (1 + 15 ÷ 100)
240 × 1.15 = 276

The new value is $276.

You can also calculate the increase separately:

240 × 15 ÷ 100 = 36
240 + 36 = 276

The multiplier method is often faster. A 5% increase uses a multiplier of 1.05, a 12% increase uses 1.12, and a 30% increase uses 1.30.

Finding the original value before an increase

If you know the new value and the percentage increase but not the original amount, rearrange the formula:

Original value = New value ÷ (1 + Percentage increase ÷ 100)

For example, a new price is $92 after a 15% increase. The original price was:

92 ÷ 1.15 = 80

The original price was $80.

This calculation is important because subtracting 15% directly from $92 would be incorrect. The 15% increase was calculated from the original $80, not from the final $92.

Percentage increase versus percentage points

Percentage increases and percentage-point increases are different.

Suppose a conversion rate rises from 4% to 5%. The change is 1 percentage point because:

5% − 4% = 1 percentage point

But the relative percentage increase is:

(5 − 4) ÷ 4 × 100 = 25%

So the conversion rate increased by 1 percentage point, or 25% relative to its original rate. Use percentage points when comparing percentages directly, and use percentage increase when measuring the relative change from the starting percentage.

How to check your answer

A quick reverse check can catch many mistakes. If the original value is $75 and the increase is 20%, calculate 20% of $75:

75 × 0.20 = 15
75 + 15 = 90

The result matches the new value of $90.

You can also check using the multiplier:

75 × 1.20 = 90

If your calculated percentage does not recreate the new value, review the subtraction, decimal placement, and denominator. Keep extra decimal places during the calculation and round only at the end when accuracy matters.

Common mistakes and how to fix them

Dividing by the new value

A frequent error is dividing the increase by the new value. For a change from 80 to 100, someone might calculate 20 ÷ 100 = 20%. The correct calculation is 20 ÷ 80 = 25% because the comparison is based on the starting amount.

Forgetting to multiply by 100

If the calculator displays 0.18, that is a decimal representation of 18%, not 0.18%. Multiply by 100 or move the decimal point two places to the right.

Reversing the subtraction

For an increase, calculate new minus original. If you calculate original minus new, you will get a negative result. A negative answer usually indicates a decrease or a reversed subtraction order.

Using the wrong original value

For multiple changes, the relevant original value is normally the value at the beginning of the comparison period. If a price changes from $50 to $60 and then to $66, the increase from $50 to $66 is 32%, while the second change from $60 to $66 is 10%.

Rounding too early

If the values produce a long decimal, keep the full calculator result until the final step. Early rounding can slightly change the answer, especially in financial, scientific, or statistical work.

Confusing a percentage increase with an added percentage

A 20% increase is not the same as adding 20 units. The increase depends on the original value. Twenty percent of $50 is $10, while 20% of $500 is $100.

Calculating an increase when the result is negative

If the new value is lower than the original, the same formula produces a negative percentage. For example, a quantity falling from 200 to 150 gives:

(150 − 200) ÷ 200 × 100 = −25%

The negative sign indicates a decrease of 25%. When reporting the result in plain language, say that the value decreased by 25% rather than describing it as a negative increase.

Limitations and special cases

The standard formula requires a meaningful original value. If the original value is zero, division by zero is undefined, so a conventional percentage increase cannot be calculated. In that situation, report the absolute change or use a different measure appropriate to the context.

Negative starting values also require care. The mathematical formula can produce a result, but describing it as a percentage increase may be misleading when comparing debts, temperatures, account balances, or profit and loss figures that cross zero. Explain the actual values and the direction of change instead of relying on the percentage alone.

For averages, rates, or totals collected over different time periods, check that the measurements are comparable. A rise in total sales may reflect a longer reporting period rather than an actual increase in performance. Percentages describe the numerical change, but they do not explain why the change occurred.

Taxes, discounts, fees, and successive increases may compound. A 10% increase followed by another 10% increase produces a total increase of 21%, not 20%:

1.10 × 1.10 = 1.21

The second 10% is applied to the already increased amount. Use multipliers when several percentage changes happen in sequence.

A simple checklist

Before accepting your answer, confirm the following:

You identified the original and new values correctly.
You calculated new value minus original value.
You divided by the original value.
You multiplied by 100.
You rounded only after completing the calculation.
You used percentage points instead of percentage increase when comparing two rates directly.
You checked the result by applying the percentage back to the original amount.

For most everyday comparisons, enter (new − original) ÷ original × 100 into your calculator. Once you remember that the original value is the denominator, calculating percentage increases becomes a quick and dependable process.