Inside PAYBACK: the maths behind an SEO fix's payback period

Short answer: a technical SEO fix is an investment with a payback period, and you can work that period out on one line. PAYBACK takes a fix's extra clicks, turns them into conversions and money, compares that with what the fix costs, and tells you how many months it takes to earn the cost back. It does this three times: worst, base and best case. No black box. You can check every number below with a calculator.

For the wider question of measuring SEO ROI, read how to measure SEO ROI. This piece is the model itself.

The model, line by line

1. Extra clicks per month. PAYBACK has two ways to get this number:

• Traffic mode: pages x clicks per page x uplift %. Leave pages blank and the clicks figure is treated as total monthly clicks.
• CTR change mode: impressions x (new CTR - current CTR). Use it when the fix is a title or snippet change.

2. Conversions. Extra clicks x click-to-partner % x conversion rate. The partner rate is for lead forms, checkouts and click-outs. It defaults to 100%.

3. Monthly value. Conversions x value per customer. Value can differ per case.

4. Cost. Days x rate + other costs.

5. Simple payback, the headline. Cost / monthly value at full effect. If you choose a revenue-share deal, its delay in months is added on top.

6. Ramp-adjusted payback, the honest one. Fixes don't land at full strength on day one. Value builds up in a straight line over the ramp months. PAYBACK steps through up to 36 months and finds the month where the running total passes the cost.

7. Year one. The running total at month 12 minus the cost.

The verdict

You set a payback window, 12 months by default. The verdict rule is strict on purpose:

• Pays back in the base case inside the window: you get "Pays back in X months (base case)".
• Only the best case pays back inside the window: you get "Only pays back in the best case".
• Neither does: you get "Not worth doing at these assumptions".

The worst case is there to keep you honest, not to decide.

Edge cases

• A cost of zero or less reports zero payback, and the timeline says "no cost entered", so a free fix doesn't look like a miracle.
• A monthly value of zero means payback is "never", shown as "over 36 months" on the ramped view.
• Revenue share pushes value out by the delay you enter before any ramp starts.
• Defaults are starting guesses, not benchmarks. The starting numbers that GONE and BOTCHECK hand over say so in the code. Replace every one with your own numbers.

Worked example

These are PAYBACK's own Sample input numbers. They're assumptions, not measurements.

pages ............ 120
clicks per page .. 45 a month
uplift ........... worst 3%  | base 8%   | best 15%
conversion ....... worst 1.2%| base 1.8% | best 2.4%
value ............ 60 per customer
ramp ............. worst 4   | base 3    | best 2 months
fix cost ......... 3,300 in total

Base case by hand:

• 120 x 45 = 5,400 clicks a month.
• 8% of that is 432 extra clicks.
• At 1.8%, that's 7.78 conversions.
• At 60 each, that's 466.56 a month.
• 3,300 / 466.56 = 7.07 months simple payback.

With the 3-month ramp, the running total passes 3,300 at about 8.1 months.

The best case pays back in about 2.8 months and the worst case in about 28.3. That spread is the point. If the decision only works in the best case, you don't have a business case yet. You have a hope.

Run it: open PAYBACK with this Sample input

The money angle

This is the tool I use to argue with myself before I argue with a client. It turns "we should fix the redirect chains" into "this pays back in a quarter in the base case, and here is every assumption". That's language a finance director signs off on.

Feed it real inputs: GONE and BOTCHECK hand over their fix groups, and the CTR curve gives you a site-specific base case for CTR changes. Then rank by base-case payback, not by how interesting the fix is.

If you want the maths run across a whole site's backlog, that's a technical SEO audit.