How to Calculate Percentage Increase, Decrease & Markup for Business

September 5, 2026 · 5 min read

Percentages are the language of business. Margins, markups, discounts, growth rates, commissions, tax rates — they all run on percentage calculations. Getting them wrong means pricing errors, lost profits, and inaccurate forecasts. Getting them right takes seconds with the right tool.

Percentage Increase

The formula is: ((New Value - Old Value) / Old Value) × 100. If your revenue went from $10,000 to $12,500, the percentage increase is ((12,500 - 10,000) / 10,000) × 100 = 25%. This is essential for measuring growth in revenue, traffic, conversions, and any business metric.

Percentage Decrease

Same formula, but the result is negative. Revenue dropped from $12,500 to $10,000? That is ((10,000 - 12,500) / 12,500) × 100 = -20%. Note that a 25% increase followed by a 20% decrease brings you back to the same number — the percentages are not symmetrical.

Markup vs Margin — The Critical Difference

Markup is calculated on cost: a $10 item sold at $15 has a 50% markup. Margin is calculated on selling price: the same sale has a 33.3% margin. Confusing the two is one of the most expensive mistakes in small business. If you set prices using margin when you meant markup, you are making less profit than you think.

Quick Percentage Shortcuts

10% of any number: move the decimal one place left. 5%: take 10% and halve it. 15%: take 10% plus 5%. 20%: take 10% and double it. 25%: divide by 4. These mental shortcuts are useful for quick estimates — use the calculator for exact figures.

Try It Now

Our free Percentage Calculator handles this instantly — no signup, no limits.

Also useful: our Profit Margin Calculator for related calculations.