How to Calculate Cost per Signed Case for a Law Firm
Cost per signed case connects marketing spend to the outcome that matters: retained clients. Here is the formula, the inputs most firms miss, and a practical method for using the number without fooling yourself.
Category: Measurement | 2026-08-31 | 10 min read | By Lotus Signal
Why cost per lead is not enough
Cost per lead measures how efficiently a channel creates inquiries. Cost per signed case measures whether the entire growth system creates clients. That distinction matters because marketing does not stop at the form fill or phone call. A lead still has to be answered, qualified, scheduled, followed up with, and retained. Two channels can produce leads at the same price and produce very different case economics.
Use two versions of the formula
A useful reporting system separates channel performance from the fully loaded cost of growth. Channel cost per signed case divides direct channel cost by signed cases attributed to that channel — use it to compare controllable acquisition channels. Blended cost per signed case divides total acquisition cost by all marketing-sourced signed cases — use it for executive planning. Do not mix these two numbers.
- Channel cost = direct channel cost / signed cases attributed to that channel
- Blended cost = total acquisition cost / all marketing-sourced signed cases
- Channel cost helps decide what to fund, fix, or cut
- Blended cost helps decide whether the overall growth engine is sound
A six-step calculation that holds up in a partner meeting
Step 1: Define a signed case — choose one operational event and use it everywhere. Step 2: Choose a measurement window and respect case lag — a lead generated on the last day of August may sign in September. Step 3: Build the cost numerator — include only costs governed by a documented rule. Step 4: Preserve source data through intake — every inquiry needs a durable lead ID, original source, and final disposition. Step 5: Count signed cases by source and cohort — use standardized dispositions. Step 6: Calculate and reconcile — divide cost by signed cases and compare with the prior period.
A worked example — the number and the leak
Consider a firm that spends $25,000 in one month and generates 200 inquiries. Ten of those inquiries become signed cases. Cost per lead is $125, lead-to-signed-case rate is 5%, and cost per signed case is $2,500. Now assume better response and follow-up raise the signed cases from that cohort to 13. The cost per signed case becomes about $1,923 without buying another lead. A lower cost per signed case can come from cheaper traffic, better-fit leads, faster intake, stronger consultation execution, or better follow-up.
What is a good cost per signed case?
There is no responsible universal number. A tolerable acquisition cost depends on practice area, case mix, market, fee model, time to revenue, fulfillment cost, capacity, and risk. Set an internal ceiling from your own economics: estimate case value, subtract direct delivery costs and overhead, decide the contribution margin the firm requires, and the remainder is the maximum sustainable acquisition cost. Use separate targets for materially different case types.
How to use the metric without cutting future growth
Cost per signed case is a decision metric, not an automatic kill switch. Before cutting a channel, ask whether source tracking is complete, whether the lead cohort has had enough time to mature, whether all channel costs are included consistently, whether intake answered and followed up at the expected standard, and whether a few high-value case types are hidden inside a blended average.