How to Calculate Your Break-Even Cost per Lead

Every lead source has a price at which it stops making you money. Most contractors never calculate it, so they judge vendors by feel — "that seems expensive" — rather than by math. The break-even cost per lead gives you a hard ceiling, and a target below it, for any source.

The formula

You need five numbers from your own records:

• Average job size (sold revenue per job)
• Gross margin (revenue minus direct job costs like materials, labor, permits, and sales commissions, as a percentage)
• Contact rate (leads you actually reach)
• Booking and show rate (reached leads that become sits)
• Close rate (sits that become sales)

Then:

1. Gross profit per job = average job size × gross margin
2. Lead-to-sale rate = contact rate × booking rate × show rate × close rate
3. Break-even cost per lead = gross profit per job × lead-to-sale rate

At that price, acquisition consumes all the gross profit from the job, leaving nothing for overhead or profit. Your target cost per lead should be a fraction of break-even — the share of gross profit you're willing to spend to acquire a customer.

A worked example

Illustrative roofing contractor:

• Average job: $15,000
• Gross margin: 40% → $6,000 gross profit per job
• Contact rate 75%, booking rate 45%, show rate 80%, close rate 30%
• Lead-to-sale rate: 0.75 × 0.45 × 0.80 × 0.30 ≈ 8.1%

Break-even cost per lead ≈ $6,000 × 8.1% ≈ $486.

If this contractor is willing to spend 25% of gross profit on acquisition, the target is about $120 per lead. A $90 lead is attractive; a $200 lead is profitable only if it converts better than this contractor's average.

The same math for appointments and sits

Drop the steps the vendor handles:

• Break-even cost per appointment = gross profit per job × show rate × close rate
• Break-even cost per sit = gross profit per job × close rate

Using the example: break-even per sit ≈ $6,000 × 30% = $1,800; at a 25% target share, about $450 per sit. That's how you judge an appointment setting quote.

Sensitivity: how close rate and job size move the ceiling

Target cost per sit at 25% of gross profit, 40% margin:

Two lessons jump out. First, improving close rate raises what you can afford as much as raising prices does. Second, small-ticket trades must be far stricter about acquisition costs than big-ticket ones.

What to include in gross margin

Be honest here, or the formula flatters bad sources:

• Include: materials, crew labor, subcontractors, permits, disposal, sales commissions tied to the job, financing fees you absorb.
• Exclude: overhead like office rent and admin salaries — that's what your remaining gross profit must cover.

Using break-even in practice

• Set a target per source before you buy, not after.
• Recalculate quarterly as margins, close rates, and job sizes shift.
• Measure over a full sales cycle, since some sales close weeks after the appointment.
• Account for lifetime value cautiously. Repeat work and referrals can justify paying more for a first job, but don't count on them until you've measured them. See customer lifetime value.

To put this into a reusable spreadsheet, follow the lead ROI calculator guide. For the company-wide view, see contractor customer acquisition cost.