Should I use revenue or profit margin in this calculation?

Contribution margin — revenue minus the direct cost of doing that specific job — not total revenue and not your fully overhead-loaded profit number. Using revenue overstates what you can afford to spend on lead acquisition.

How do I find my real close rate if I've never tracked it?

Pull your last 90 days of leads from whatever system holds them (CRM, spreadsheet, even a call log) and divide jobs won by total leads received in that period. It won't be perfectly precise the first time, but it's far better than guessing.

What profit buffer percentage should I use?

It depends on your business and how thin your margins already run, but most service businesses use somewhere between 30% and 50% as a buffer, reserving that portion of expected value per lead as required profit rather than spending it all on acquisition.

Does this formula change for businesses with recurring revenue instead of one-time jobs?

Yes — for recurring-revenue businesses, use customer lifetime contribution margin instead of a single job's margin, since the real value of a lead includes every renewal, not just the first sale.

How often should I recalculate my max cost per lead?

Quarterly at minimum, or immediately after any meaningful change to your pricing, direct costs, or sales process — all three inputs can shift enough in a few months to change the ceiling significantly.

GrowthJan 27, 2026

What Can You Actually Afford to Pay for a Lead?

You can afford to pay, at most, your average job's profit contribution multiplied by your close rate, minus the profit margin you actually need to keep — and most businesses have never run that number, so they either overpay for leads that can't be profitable, or underbid on ad spend that would have paid for itself. This is a five-minute calculation once you have the three real inputs.

Why Do Most Businesses Get This Number Wrong?

The common mistake is comparing cost-per-lead across channels without ever asking what a lead is actually worth. A $40 lead sounds expensive next to a $12 lead — until you learn the $40 lead closes at 35% and the $12 lead closes at 4%. Cost per lead means nothing without close rate and job value attached to it.

What's the Actual Formula?

Max affordable cost per lead = (average job contribution margin × close rate) − required profit buffer. Contribution margin is revenue minus the direct cost of doing that job — materials, labor, subcontractors — not your full overhead-loaded number. Close rate is the real percentage of leads that become paying jobs, not the percentage of quotes you send that get accepted.

Can You Walk Through a Real Example?

Input	Example Value
Average job revenue	$2,400
Direct job cost	$1,500
Contribution margin	$900
Lead-to-close rate	15%
Expected value per lead	$135
Required profit buffer (40%)	$54
Max affordable cost per lead	$81

In this example, a channel delivering leads at $60 each is profitable with room to spare. A channel at $95 each is losing money on every lead, even though $95 might look reasonable compared to industry averages you've seen quoted elsewhere.

What's the Most Common Input Mistake?

Using revenue instead of contribution margin. A business that quotes an average job at $2,400 but only nets $900 after direct costs will dramatically overpay for leads if it calculates against the full $2,400 — that's the single most common way this math gets misused, and it's an easy trap because revenue is the number everyone already has memorized.

How Does Close Rate Change This Number Month to Month?

Close rate isn't fixed. A slower response time, a change in the sales team, or a shift in lead quality from a new channel can move your real close rate meaningfully within a quarter. Recalculating this number quarterly, not once and forgetting it, is what keeps ad spend decisions grounded in current reality instead of a number from six months ago.

How Do You Use This Number to Actually Decide Where to Spend?

Once you know your ceiling, compare it against the real, tracked cost per lead of each channel — not the platform's reported cost, your actual tracked cost including any agency fee. Anything meaningfully under the ceiling is worth scaling; anything over it needs either a lower acquisition cost or a higher close rate before it deserves more budget. Our growth work starts with exactly this calculation before recommending where a single dollar goes.