Free tool · CPC · CPA

CPC and CPA calculator.

What each click and each result costs you, and the most you can afford to pay for either.

Runs in your browser. Nothing is uploaded or stored.
  1. 1Type your own numbers on the left. Everything updates as you type.
  2. 2Read the results on the right. The highlighted figure is the one that matters most.
  3. 3Copy the link to share these exact numbers, or switch currency at the top.

From your campaign

What you can afford

Cost per acquisition–

Turns green when it is under your maximum.

Cost per click–
Conversion rate–
Max CPA you can afford–
Max CPC you can afford–

Exchange rates: fallback table dated 2026-10-01. Live rates load from Frankfurter when available.

The formulas

CPC = ad spend ÷ clicks
CPA = ad spend ÷ conversions
Max CPA = conversion value × margin
Max CPC = max CPA × conversion rate

Worked example

A plumber spends £500 on Google Ads, gets 400 clicks and 10 enquiries. CPC is £1.25, CPA is £50 and the site converts 2.5% of clicks. If an average job is worth £400 at a 30% margin, each enquiry is worth up to £120, so a £50 CPA is comfortable. The most the plumber can bid per click is £120 × 2.5% = £3. If a competitor pushes CPCs past that, the answer is a better landing page (raising the 2.5%), not a bigger bid.

Lead quality changes everything

If only one in four enquiries becomes a job, the max CPA drops to £30. Feed closed deals back into Google and Meta as offline conversions and the platforms will optimise towards the enquiries that actually turn into work. That is what we built for West of Brickell Homes.

FAQ

CPC & CPA calculator: questions answered.

What is CPC?

Cost per click: total ad spend divided by clicks. £500 of spend for 400 clicks is a £1.25 CPC.

What is CPA?

Cost per acquisition, also called cost per conversion or cost per result: ad spend divided by the number of sales or leads. £500 of spend for 10 enquiries is a £50 CPA.

What is the CPA formula?

CPA = ad spend ÷ conversions. To work out the most you can afford: max CPA = value of a conversion × profit margin.

How do CPC and CPA connect?

CPA = CPC ÷ conversion rate. A £1.25 CPC at a 2.5% conversion rate gives a £50 CPA. Halve the CPC or double the conversion rate and CPA halves.

What is a good cost per lead?

The one that leaves you profitable after the leads that don't close. If one in five leads becomes a £400 job with a 40% margin, each lead is worth £32, so anything under that is good.

Why is my CPA higher than my CPC × conversion rate suggests?

Usually because conversions are being double counted, or tracked conversions include low-value actions like page views. Check that only real enquiries or sales count as conversions.

Should I bid manual CPC or use smart bidding?

With reliable conversion tracking and at least 30 conversions a month, target CPA or target ROAS bidding usually beats manual. Below that, manual or maximise clicks with a bid cap gives more control.

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