Percent Change in Volume: Formula and Example

This calculator finds the percent change between an original volume and a new volume, showing how much the quantity increased or decreased relative to its starting value. Enter both volumes in the same unit to get the signed percentage change and the absolute difference.

Formula

Percent change = (new volume − original volume) ÷ original volume × 100

• Original volume is the starting amount, in any volume unit.
• New volume is the later or comparison amount, in the same unit.
• Percent change is the relative change, expressed as a percentage. A positive result means an increase; a negative result means a decrease.

The volume difference is new volume − original volume. It is an absolute change, not a percentage. The calculator reports that difference in liters because the input fields are labeled in liters. The percent result does not have a volume unit.

Worked Example

Using the calculator’s default values, the original volume is 10 L and the new volume is 12 L.

1. Subtract the original from the new volume: 12 L − 10 L = 2 L.
2. Divide the difference by the original volume: 2 L ÷ 10 L = 0.2.
3. Multiply by 100: 0.2 × 100 = 20%.

The volume increased by 20%. The absolute difference is 2.00 L.

What You’ll Need

• The original volume before the change.
• The new volume after the change.
• A way to confirm both measurements use the same unit, such as liters, milliliters, cubic centimeters, gallons, or cubic feet.

Step-by-Step

1. Identify the starting volume. Use the original or earlier measurement as the denominator. Percent change is measured relative to this starting point, not the new value.
2. Record the new volume. This is the later measurement or the amount you want to compare with the original.
3. Make the units match. Convert one measurement if needed before calculating. For instance, convert 500 mL to 0.5 L before comparing it with a volume recorded in liters. For US customary measures, convert quarts to gallons or cubic inches to cubic feet as appropriate. Do not mix US gallons with imperial gallons; they are different units.
4. Subtract the original from the new. Calculate new volume − original volume. Keep the sign: a result above zero indicates an increase, while one below zero indicates a decrease.
5. Divide by the original volume. This makes the difference relative to the starting amount. Do not divide by the new volume or by the difference.
6. Multiply by 100. This converts the decimal ratio into a percentage. For example, 0.2 becomes 20%, while −0.2 becomes −20%.
7. Round only at the end. Keep extra digits during intermediate calculations, then round the final percentage to a sensible number of decimal places. State the sign or write “increase” or “decrease” so the direction is clear.

Common Mistakes

• Reversing the values: The standard formula is (new − original) ÷ original × 100. Reversing the subtraction changes an increase into a decrease.
• Using the wrong denominator: Divide by the original volume. Dividing by the new volume calculates a different comparison, not standard percent change.
• Mixing units: A value in milliliters cannot be directly compared with one in liters. Convert first, even if the numbers look similar.
• Dropping the negative sign: A negative result is meaningful: it indicates that the new volume is lower. Report it as a decrease rather than changing it to a positive number.
• Confusing percent with volume: A change of 2 L is an absolute difference; a change of 20% is relative to the original amount. Include the appropriate unit or percent sign.
• Rounding too early: Early rounding can noticeably affect results when volumes are small or close together. Use the full measurements for the calculation and round the final answer.

Tips

• Write down which measurement is original and which is new before entering numbers, especially when checking several time periods.
• Keep the absolute difference alongside the percentage when it helps explain the scale of the change. A small percentage can represent a large amount if the original volume is large, and vice versa.
• Use consistent measurement precision. If your measuring tool only supports whole milliliters, reporting a result to many decimal places suggests more certainty than the measurements provide.
• For a sequence of changes, use each period’s starting volume as that period’s original value. Successive percentage changes are based on changing starting amounts and should not simply be added.
• When communicating the result, include the two volumes, their units, the direction, and the rounded percent. For example: “The volume rose from 10 L to 12 L, an increase of 20%.”

Troubleshooting

The calculator shows an error or undefined result: Check whether the original volume is zero. Percent change from zero is undefined because the formula requires division by the original value. If the starting volume is zero, report the absolute difference instead, or describe the change without a percent.

The result has the wrong direction: Check that the earlier amount is entered as the original and the later amount as the new value. If the new volume is smaller, the result should be negative.

The result seems far too large or small: Check for a unit conversion error and confirm that you divided by the original volume. Also check whether a decimal point or a unit prefix such as milli- was entered incorrectly.

The result differs slightly from another calculation: Compare the unrounded intermediate values and the number of decimal places used. Different rounding conventions can cause small discrepancies.

Frequently Asked Questions

Can percent change in volume be negative?
Yes. A negative result means the new volume is smaller than the original, so the volume decreased.

What if the original volume is zero?
The percentage is undefined because the formula divides by the original volume. Report the absolute change or explain the amounts directly instead.

Does the unit affect the percent change?
No, provided both volumes use the same unit. Converting both measurements from liters to milliliters changes their numerical values but not the percentage.

Is percent change the same as percent difference?
No. Percent change uses a designated original value as its reference. Percent difference is a separate comparison that typically uses the average of two values as the reference.

How do I calculate percent decrease?
Use the same formula: (new − original) ÷ original × 100. When the new volume is lower, the answer is negative; its magnitude gives the decrease percentage.

Can the percent change be more than 100%?
Yes. If the new volume is more than twice the original, the increase exceeds 100%. For example, going from 10 L to 25 L is a 150% increase.

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in old | Original volume | L | 10 | 0
in new | New volume | L | 12 | 0
out change | Percent change | % | (new - old) / old * 100 | 2
out difference | Volume difference | L | new - old | 2