Percentage
A percentage says how many parts out of every 100 something is. You get it by dividing the part by the total and multiplying by 100: 45 out of 180 customers is 45 ÷ 180 × 100 = 25%.
Select any words here to ask your Maestro about them.
180 customers bought in October; 60 of them used a coupon. 45 came back, all from the coupon group. The report says: "75% came back to buy again." Which total do you think that's out of?
How to work it out: divide the part by the total and multiply by 100. If 45 of 180 customers came back, 45 ÷ 180 = 0.25, and 0.25 × 100 = 25%. For the question the other way around (what's 15% of $840?), multiply: 840 × 15 ÷ 100 = $126.
What goes wrong most isn't the math; it's the total. The same number can be 25% or 75% depending on what you compare it to, as in the figure. Before you trust a percentage, ask "of what?". When a percentage moves from one month to the next, measure the move with percent change.
In Excel: type =B2/C2 and apply percent format. Don't multiply by 100 in the formula, because the format already does.
Practice it in 43% of what? How to tell what total a percentage is out of.
How it's used
The two questions everyone asks
How to work out a percentage
- What percent of 180 is 45? 45 ÷ 180 = 0.25Part over total. The total always goes on the bottom.
- marked: 0.25 × 100 = 25%
- In Excel: =B2/C2, then Home › Percent StyleThe format multiplies by 100 when it displays the cell; don't do it yourself.
- marked: What's 15% of $840? 840 × 15 ÷ 100 = $126
- In Excel: =840*15%Excel reads 15% as 0.15.
When to look closer
Why does Excel show 2500%?
Cell D2
- marked: =B2/C2*100
- 25
You typed =B2/C2*100 and got 25. If you apply percent format, what do you think the cell shows?
Ask your Maestro about Percentage
It answers from the free course page closest to this word, the way it answers while you study.
You: What does "Percentage" mean, in plain words?
Your Maestro: I'll explain it with a case of yours: it sticks better than a definition. Which percentage do you use at work without knowing what it's out of?
Asking about: Answers from the page "How do I show each group's total next to every row in SQL?"
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Related terms
- Percent change
Percent change says how much a number moved relative to where it started: (new − old) ÷ old × 100. If sales go from $80K to $100K, they're up 25%.
- Weighted average
A weighted average gives each value a weight for how much it counts, instead of treating them all the same: multiply each value by its weight, add them up and divide by the sum of the weights.
- KPI (key performance indicator)
A KPI is a number a team tracks to know whether it's doing well at what matters most, like monthly sales or orders delivered on time. It only works if it's well defined, so two people who calculate it get the same answer.