Billable hours

Billable hours are the time entries you can legitimately invoice a client for, measured in the increment your contract specifies — typically 0.1h (6 minutes, law firms) or 0.25h (15 minutes, most agencies) or 1.0h (some fixed-fee engagements).

The gap between billable hours tracked and billable hours actually worked is the primary financial leak in every agency and professional-services firm. Most firms running manual timesheets understate billable time by 10–30%.

Worked example

A consulting engagement at $200/hr with a 0.25h minimum increment:

• You take a 17-minute Slack call about the project. → Rounds to 0.25h billable = $50.
• You spend 2h 42min on a deliverable. → Rounds to 2.75h billable = $550.
• You have a 6-minute internal discussion that you decide to write off. → 0h billable = $0.

The aggregate of all such decisions over a month — what to include, what to round, what to write off — is where agencies lose money. Time tracking software with real-time timers captures entries at the moment they happen, before the “I’ll add that later” forgetting curve removes them.

Why agencies typically lose 10–30% of billable hours

1. Short tasks below the mental billing threshold. A 10-minute email exchange about a project feels too small to bill. With 8 of these per day at $200/hr, that’s $267 in daily write-offs — or $5,600/month at a 5-person agency.
2. Context-switching between projects. Every time you switch tasks, the previous task’s timer needs to stop and the new one needs to start. Manual reconstruction at end-of-day consistently under-captures these switches.
3. The “rounding down” instinct. Professionals chronically round billable time down, not up. The 43-minute call becomes “about 40 minutes” which becomes “0.5h” on a 0.25h increment.

The billable hours formula

Billable utilization rate = (Billable hours tracked ÷ Total available hours) Ã- 100%

A 40-hour work week with 28 billable hours = 70% billable utilization. Most creative agencies target 65–75%. Law firms target 80–90%.

Realization rate = (Hours invoiced ÷ Hours tracked as billable) Ã- 100%

If you tracked 28 billable hours but invoiced for 25 (wrote off 3 for client relations), realization is 89%. Low realization indicates over-discounting or poor scope management.

Related concepts

• Timesheet — the record system for capturing billable hours
• Payroll integration — for converting tracked hours to payroll
• Project tracking — organises billable hours by project and client

Tools that track billable hours accurately

• Toggl Track review — best overall for agency billable hour capture
• Harvest review — best when billable hours drive invoices directly
• Clockify review — best free option for freelancers tracking billable time