Cost per click tells you what each visit from a paid ad actually costs. It is a simple division, but it becomes far more useful when you can also derive it from CPM and click-through rate, because that shows which lever moves it.
How it works
CPC = total ad spend / number of clicks. The related formulas are: CTR = clicks / impressions x 100, and CPC = CPM / (CTR x 10) when CPM is cost per thousand impressions and CTR is a percentage. Equivalently, CPC = CPM / (1000 x CTR as a decimal). A high CPC is not automatically bad; it depends on what each click is worth to you in sales or leads.
Step by step
- Write down total ad spend for the period.
- Write down total clicks for the same period.
- Divide spend by clicks for CPC.
- If you only have CPM and CTR, use CPC = CPM / (1000 x CTR as a decimal).
- Compare CPC with revenue per click or value per lead to judge it.
- Track CPC by campaign and device, not only as one blended number.
Worked example
You spend $500 and get 250 clicks. CPC = 500 / 250 = $2.00 per click. From CPM and CTR: a campaign with a $20 CPM and a 2 percent CTR gives CPC = 20 / (1000 x 0.02) = 20 / 20 = $1.00. If each click converts at 5 percent and each sale is worth $100 profit, revenue per click is $5.00, so a $2.00 CPC leaves $3.00 per click before other costs.
Common mistakes
- Dividing clicks by spend instead of spend by clicks, which gives clicks per dollar, not CPC.
- Mixing periods, such as spend from one month with clicks from another.
- Judging CPC without conversion value. A $5 click that sells is better than a $0.50 click that never converts.
- Using CTR as a percentage in the decimal formula without converting, which makes CPC 100 times too small.
Try it with the free tool
You can follow every step above by hand, but the free tool below does the same calculation instantly. Try your own numbers in it, then check one result by hand so you trust the method as well as the answer. Open the full tool here: open the tool.
Checklist before you finish
- Write down every input number first, with its unit, before you calculate anything.
- Work through the steps in order, and do not skip the unit conversions.
- Check the answer against the worked example above: is it the right size, and does the direction make sense?
- Round only at the end, and keep the unrounded figure for any follow-up calculation.
Practice with your own numbers
Pick three cases of your own and work each one by hand. First, try a simple round-number case you can check mentally. Second, try a realistic case with awkward numbers, the kind you will actually meet. Third, try an edge case, such as a very small or very large input, and confirm the answer still behaves sensibly. If any case gives a surprising result, re-check the units and the formula step by step before you trust it.
If your answer looks wrong
Most errors come from a small set of causes. Check that you used the same units throughout, that you divided where the formula divides and multiplied where it multiplies, and that you applied any percentage as a decimal. Check the order of operations: powers and brackets come before multiplication and division, which come before addition and subtraction. Finally, test the method on the worked example in this guide. If your method reproduces the example answer, the method is right and the inputs deserve a second look.
Quick tips
If CPC rises, check whether CTR fell or CPM rose first, because the fix differs. Improve the ad and landing page for CTR, or narrow targeting and timing for CPM.