how to calculate percentage improvement

Quick answer: the formula for percentage improvement

In most everyday situations, percentage improvement is calculated by comparing the change to the original value:

Percentage improvement = ((New Value - Original Value) / Original Value) × 100

This is the same calculation often called percentage increase when bigger is better. If the result is negative, it means performance got worse (or there was a decrease).

Step-by-step method

1) Find the difference

Subtract original value from new value.

Difference = New - Original

2) Divide by the original value

This turns the difference into a relative change.

Relative change = Difference / Original

3) Multiply by 100

Convert to a percentage.

Percent change = Relative change × 100

Examples of percentage improvement

Example 1: Test score improvement

A student improves from 70 to 84.

• Difference: 84 - 70 = 14
• Relative change: 14 / 70 = 0.2
• Percentage improvement: 0.2 × 100 = 20%

Example 2: Monthly sales growth

Sales increase from $12,000 to $15,000.

• Difference: 15,000 - 12,000 = 3,000
• Relative change: 3,000 / 12,000 = 0.25
• Percentage improvement: 0.25 × 100 = 25%

Example 3: Running time (lower is better)

Time drops from 50 minutes to 45 minutes. Because lower time is better, improvement is based on reduction:

• Reduction: 50 - 45 = 5
• Relative reduction: 5 / 50 = 0.1
• Performance improvement: 0.1 × 100 = 10%

Note: standard percent change from 50 to 45 is -10%. That negative sign means the value decreased. In performance terms, that decrease is an improvement.

Common mistakes to avoid

• Using the new value in the denominator instead of the original value.
• Confusing percentage points with percent change. Going from 40% to 50% is a 10-point increase, but a 25% relative increase.
• Ignoring direction. For metrics like error rate or completion time, lower values can mean improvement.
• Forgetting the original value cannot be zero in the standard formula. Division by zero is undefined.

What if the original value is zero?

If the original value is 0, standard percentage improvement is not defined because you cannot divide by zero. In reporting, you can:

• Use absolute change instead of percent change, or
• State that growth is “from zero” and report actual units.

Spreadsheet formulas (Excel / Google Sheets)

If original value is in cell A2 and new value is in B2:

• Percent change: =(B2-A2)/A2
• Format the cell as Percentage.
• For “lower is better” improvement: =(A2-B2)/A2

When to use percentage improvement

Percentage improvement is useful because it makes fair comparisons across different scales. A $500 increase means one thing on a $1,000 baseline and something very different on a $50,000 baseline.

• Business metrics: revenue, leads, conversion rate
• Personal finance: income, savings rate, debt reduction
• Health and fitness: pace, weight lifted, resting heart rate
• Operations: defect rates, processing time, support ticket resolution

Final takeaway

To calculate percentage improvement, always compare the change to the starting value. Keep direction in mind: for some metrics, lower values indicate better outcomes. Use the calculator above for quick, accurate results.