A billable hour is any time you spend on a client's matter that the firm can put on an invoice. That is the whole definition. Everything else, the increments, the targets, the endless timesheet anxiety, is machinery built around that one idea. This guide walks through the machinery in plain English, and then shows you the part that actually costs firms money.
Why firms bill in six-minute increments
Almost every firm records time in tenths of an hour. A tenth of 60 minutes is six minutes, which makes it a clean unit to round to. So a quick email that took four minutes is billed as 0.1 hours; a call that ran 20 minutes is 0.4. Here is the full conversion attorneys look up constantly:
- 1–6 min0.1
- 7–12 min0.2
- 13–18 min0.3
- 19–24 min0.4
- 25–30 min0.5
- 31–36 min0.6
- 37–42 min0.7
- 43–48 min0.8
- 49–54 min0.9
- 55–60 min1.0
The rounding cuts both ways, but it mostly cuts against the firm. Ten separate two-minute interruptions, each rounded to 0.1, could bill as 1.0 hour if captured, or as nothing at all if you forget them by the time you fill in your timesheet. Which brings us to the number that surprises everyone.
How many billable hours are really in a day?
Far fewer than the hours you work. An attorney can sit at their desk for ten hours and record only three as billable. Industry benchmarks bear this out:
Some of that gap is legitimate: not everything you do is client-billable work. But a large slice is billable work that simply never got recorded. That is not a targets problem or an effort problem. It is a capture problem, and it is where the money is.
What the gaps actually cost
The billing rate is the number everyone stares at. The capture rate is the number that quietly determines what you take home. Try it: set your rate, a realistic number of recorded hours per day, and the realization and collection rates most firms live with. Watch what reaches the bank.
Billable-hours leakage calculator
Estimate what one timekeeper's year is worth, and how much of it quietly leaks away after the work is already done. Adjust the four inputs to match your firm.
Two things jump out when people play with this. First, nudging billable hours per day up by even half an hour changes the annual number more than most rate increases would. Second, the realization and collection sliders, the parts that happen after the work is done, take a big bite that has nothing to do with the quality of the legal work.
The hard part was never the math
Billing in tenths is arithmetic a first-year associate masters in a week. The genuinely hard part is capturing every increment accurately while you are heads-down on actual work, and then getting that time cleanly onto an invoice and collected. That is the real billable-hours problem, and it is an operational one.
Next, the behavioral half of the problem: why reconstructing your time at month-end quietly under-bills you, how automated time capture closes the gap, and the bigger picture of where revenue leaks across the whole firm.
Reclaim the hours you already worked
Caddi connects the systems where your time is spent, the phone and the inbox, to the tools you already bill from like TimeSolv and Clio, so more of your billable work actually gets recorded. See the law-firm overview, browse the operational workflows Caddi runs today, or book a demo.
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Frequently asked questions
How do billable hours work?
A billable hour is time spent on client work that a firm can invoice. Most firms record time in tenths of an hour, six-minute increments, so six minutes is 0.1 and a full hour is 1.0. Attorneys log the task, the matter, and the time, and those entries flow into the client's invoice at the attorney's billing rate. The mechanics are simple; the hard part is capturing every increment accurately as the day happens.
What is a billable hour in six-minute increments?
Firms bill in tenths of an hour because a tenth of 60 minutes is six minutes, a clean unit to round to. So 1 to 6 minutes is 0.1, 7 to 12 minutes is 0.2, and so on up to 1.0 for a full hour. A two-minute phone call and a five-minute email both bill as 0.1. Over a day of small tasks, how you round these increments adds up to real money.
How many billable hours are in a work day?
Fewer than most people expect. Even though attorneys work eight to ten hours, only a portion is client-billable work, and only some of that gets recorded. Industry benchmarks (Clio Legal Trends Report) put utilization near 31%, roughly 2.9 recorded billable hours from an eight-hour day. The rest is non-billable work, admin, and, critically, billable work that simply never got logged.
Why do attorneys lose billable hours?
The single biggest cause is not laziness or slow work; it is time that was worked but never recorded. When attorneys reconstruct their time hours or weeks later instead of logging it as it happens, memory decays and entries round down or vanish. That capture gap, not the billing rate, is where most billable revenue is quietly lost.