How much to spend on ads, reverse engineered from your close rate

How much to spend on ads when you've been stuck at the same number for years

If I told you that for every $10 you spent, you'd get $100 back, would you only spend $5? Probably not. But that's exactly how most small business owners are running ads right now.

The question of how much to spend on ads isn't a vibe. It's a math problem. And the reason you've been stuck at the same revenue for the last few years is almost always the same: you're putting the same amount in every month, so you're getting the same amount out.

I recently worked with a gym that was generating well on a monthly basis but had been at the same point for a long time. One equation fixed the ceiling. That's what I'm walking through here — how to reverse engineer your ad spend backward from a monthly revenue goal, using real numbers from your business, not made-up ones.

Why flat ad spend stalls growth (and why your market isn't static)

Here's what people forget: you're not putting the same ad in front of the same people every month. Buyers rotate in and out of your market constantly. People move into your town. People age into the decision. People who weren't ready in March are ready in October because something in their life changed.

There are in-market buyers ready to buy today, and out-of-market buyers who aren't ready yet but will respond to the right ad copy and take a first step. If your spend stays flat, you're only ever touching the same slice of that rotation. You're leaving the new entrants on the table every single month.

So before we touch the math, understand the assumption underneath it: the audience refreshes. More spend reaches more of that refresh. That's where growth comes from.

Reverse engineering a $5K per month goal from close rate backward

Let's build the stack. The goal: add $5,000 in monthly recurring revenue. The offer: a $200/month membership.

Start at the end and walk backward:

**Members needed:** $5,000 ÷ $200 = **25 new members**

**Close rate (35%):** 25 ÷ 0.35 = **72 sales calls needed**

**Show rate (75%):** 72 ÷ 0.75 = **96 booked calls needed**

**Booking rate (60%):** 96 ÷ 0.60 = **160 leads needed**

**Cost per lead ($20):** 160 × $20 = **$3,200 in ad spend**

That's the whole equation. Every KPI between a lead and a dollar, reversed. And the critical rule: use your actual numbers. Not what you think you could hit if you fixed three things. If your real close rate is 35%, plug in 35%. Aspirational math breaks the whole model.

If you want to see how your ad account should be feeding these numbers back to you in the first place, I wrote about that in closed-loop attribution for small businesses.

How to calculate ROAS — and why 1.56 to 1 can still be healthy

ROAS is revenue divided by ad spend. In the example above: $5,000 ÷ $3,200 = **1.56 to 1**.

To somebody on the outside, 1.56 to 1 looks weak. It isn't, and here's why: ROAS on the first transaction is not the full picture. You have to layer in customer lifetime value.

If those 25 members stay for 10 months at $200, that's $50,000 in lifetime revenue from $3,200 of ad spend. Suddenly that "weak" 1.56 to 1 is doing a lot of work.

This is also where you decide what to touch and what to leave alone. Show rate at 75%? Don't mess with it. Booking rate holding? Leave it. The two levers worth pulling are usually close rate and cost per lead — a more irresistible offer up front drops your cost per lead, and everything downstream drops with it. If show rate is your weak point, that's a different fix — I broke that one down in the indoctrination sequence that turned a 31% show rate into 80%.

Scaling the goal to $10K — and the capacity question nobody asks

Now double the goal. $10,000/month, same inputs, nothing improves. Here's what the stack looks like:

50 members. 143 sales calls. 191 booked calls. 319 leads. **$6,380 in ad spend.** ROAS: 1.56 to 1 — almost identical. But the return went from $1,800 over spend to $3,620. Same efficiency, bigger return.

And if cost per lead creeps up to $25 instead of $20, ad spend becomes $7,975 and ROAS drops to 1.25 to 1. Lower ratio, but you're still ahead of the $5K version on raw dollars. The data tells you to expect that drop and be fine with it.

But here's the question the spreadsheet forces you to ask: can you actually talk to 143 people this month? Can you onboard 50 new members without churn spiking? These numbers don't just test if the goal is financially realistic — they test if your team has the capacity to fulfill it. Because if lifetime value collapses because you can't service what you sold, the whole model falls apart.