Worked out below step by step, with a table of related values and a live calculator so you can change the numbers.
Answer
50%
(450 − 300) ÷ 300 × 100
→
=
Change
Step-by-step working
1. Find the difference: 450 − 300 = 150.
2. Divide by the original value: 150 ÷ 300.
3. Multiply by 100: that is a 50% increase.
Check it: 300 + 150 = 450, the new value.
Formula
percent change = (new − old) ÷ old × 100
Percent change always compares the difference against the original value, not the new one.
How the change from 300 to 450 is measured
Percentage change uses the starting value as the reference. The numerical change is 150; divide that change by the original 300, then multiply by 100.
The result is 50%. A positive answer is an increase and a negative answer is a decrease. Because the original value is the denominator, changing the direction of comparison gives a different percentage.
Reasonableness and accuracy checks
Check the order: the first number must be the original or baseline value.
Apply the calculated rate to 300; after adding the change, the value should return to 450.
If the starting value is zero, ordinary percentage change is undefined and needs a different comparison method.
Check the change with a multiplier
The ratio of the new value to the starting value is 1.5. Comparing that multiplier with 1 shows how far the new value sits above the starting value in percentage terms.
1.New ÷ original = 450 ÷ 300 = 1.5.
2.Subtract 1: 1.5 − 1 = 0.5.
3.Multiply by 100 to get 50% increase.
A second worked example
What is the percent change from 300 to 600?
(600 − 300) ÷ 300 × 100 = 100%
Find the difference: 600 − 300 = 300. Divide by the original value: 300 ÷ 300. Multiply by 100: that is a 100% increase. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer.
Change insight from 300 to 450
The numerical difference is 150, a increase. Relative to the starting value 300, that difference represents 50%. The starting value matters because percentage change measures the difference against the original baseline, not the final value.
Where percentage change is useful
Percentage change is used for price movement, growth, energy use, production, traffic and performance comparisons. It is most meaningful when the starting value is clearly defined and the direction of change is reported with the percentage.
Common mistakes to avoid
Using the final value 450 as the denominator instead of the starting value 300.
Dropping the sign or direction and therefore confusing an increase with a decrease.
Calculating a raw difference only and calling it a percentage without dividing by the original baseline first.
Questions about this calculation
Is there another way to check What is the percent change from 300 to 450?
The ratio of the new value to the starting value is 1.5. Comparing that multiplier with 1 shows how far the new value sits above the starting value in percentage terms. New ÷ original = 450 ÷ 300 = 1.5. Subtract 1: 1.5 − 1 = 0.5. Multiply by 100 to get 50% increase.
What is the most common mistake with What is the percent change from 300 to 450?
Using the final value 450 as the denominator instead of the starting value 300. After correcting that setup, verify the result independently: Check it: 300 + 150 = 450, the new value.
Can I use the same method with different numbers?
Yes. What is the percent change from 300 to 600? Find the difference: 600 − 300 = 300. Divide by the original value: 300 ÷ 300. Multiply by 100: that is a 100% increase. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer. The live calculator above lets you replace both inputs and recalculate without changing the underlying method.
How can I tell whether 50% is reasonable here?
The numerical difference is 150, a increase. Relative to the starting value 300, that difference represents 50%. The starting value matters because percentage change measures the difference against the original baseline, not the final value. Use that scale or ratio check together with the reverse calculation before reusing the result in another calculation.