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A call log is not an attribution model.
Separate the available records
A call tracking system may record the time and number of calls. An ad platform reports activity and events according to its configuration. The records may overlap without proving the cause of each call.
Match dates and definitions
Before computing cost per lead, verify that campaign spend and relevant enquiries refer to compatible reporting windows and that those enquiries are reasonably attributable to the spend. Otherwise explain the limitation instead of producing a confident but misleading ratio.
Understand the handoffs
A visitor may discover a business on social media, search the company name, read reviews and then telephone it directly. Source labels can be incomplete or ambiguous. First party CRM notes and customer conversations can improve understanding, but rarely prove every influence.
Use Bluewater’s published example carefully
The Vancouver junk removal example includes 44 calls recorded between January 1 and February 16, 2026. A Google Ads export records CA$470.95 spend from January 14 through February 14. Those are different reporting windows, so the 44 calls cannot be presented as 44 ad generated leads.
Report what is known and what is not
State the source, date range, event definition and confidence level. When the records cannot confirm booked jobs or revenue, label those outcomes unverified rather than filling in numbers.
Put the measurement to work.
Start with the information you actually have. Document what can be measured, be explicit about what cannot, and use each review to decide the next practical change.
See how Bluewater approaches this work ↗Try the enquiry calculator ↗A practical check before you trust a lead report
Here is how to apply the idea to a real local service business rather than treating it as another marketing metric.
- Compare the advertising spend and enquiries over the same reporting dates. A January to February call log cannot be divided by a shorter Google Ads spend period to claim an attributable lead cost.
- Decide what counts as a lead: all calls, first time callers, qualified enquiries or booked jobs are different measures. Record the definition beside the number.
- For a sample of enquiries, check the original source record and whether the business marked the job as booked. Label missing or uncertain sources as unknown instead of assigning credit to the ad platform.