Billable hours chart: minutes to tenths of an hour

A billable hours chart converts minutes worked into the decimal hours that go on a timesheet and an invoice. The rule behind it is that 6 minutes is 0.1 hour, so 1 to 6 minutes is recorded as 0.1, 7 to 12 minutes as 0.2, and so on up to 1.0 for 55 to 60 minutes.

Time goes on an invoice as a decimal because a decimal multiplies by the hourly rate directly. Twenty-four minutes at $250 an hour is 0.4 × $250, which is $100.

The 6-minute chart: minutes to tenths of an hour

Find the minutes you worked on the left and record the figure on the right. The chart rounds up, so any part of a 6-minute block counts as the whole block.

For work longer than an hour, keep the whole hours and look up the minutes that are left. One hour and 20 minutes is 1.0 plus 0.4, so you record 1.4.

The quarter-hour chart: 15-minute increments

A quarter-hour chart has four steps to the hour, each written to two decimal places. Like the chart above, it rounds up.

Minute-by-minute chart: 1 to 60 minutes in decimal hours

Use this chart when you bill the exact time, or when you want the decimal for a timer reading before you round it. Each figure is the minutes divided by 60, to two decimal places.

These figures are themselves rounded to two places, which matters when you add them. Three 20-minute calls recorded as 0.33 each come to 0.99 hours, although together they took exactly one hour, so add the minutes first and convert the total.

How to round a time entry

Two rounding rules are in use, and they produce different bills from the same timesheet.

Rounding up bills any part of a block as the whole block, which is how the first two charts work. On 6-minute steps, a 2-minute email becomes 0.1 and a 13-minute call becomes 0.3.

The other rule, rounding to the nearest step, bills a block only once more than half of it has been worked. The 13-minute call becomes 0.2, because it is two full blocks and one minute over, and the 2-minute email isn’t billed at all.

Say a paralegal at a legal support firm bills $150 an hour and logs 48 entries for one client in a month: 30 emails and short calls of 4 minutes each, 12 document reviews of 20 minutes each, and 6 drafting sessions of 50 minutes each. That is 660 minutes, or exactly 11 hours of work.

Rounding up adds 2.2 hours and $330 to this month’s bill, which is 20% more than the time worked. Almost half of the extra comes from the 30 short entries, which are 2 hours of work billed as 3.

Which rule you may use is decided by your engagement letter, or by the client’s billing guidelines if it has them. State the increment and the rounding rule in the letter, and apply them the same way to every entry. Nothing on this page is legal advice.

The U.S. Trustee’s guidelines for fee applications in bankruptcy cases say time entries should be kept “in time periods of tenths of an hour” (28 CFR Part 58, Appendix A, read 13 Oct 2026). The State Bar of Georgia’s Formal Advisory Opinion 01-1 (issued 3 May 2001, read 13 Oct 2026) lets a lawyer bill in standard time units as long as the fee stays reasonable and the client has been told the method. It calls a 6-minute unit preferable, and it describes repeatedly rounding one minute up to fifteen as “questionable at best”. That opinion covers Georgia lawyers, so check what your own bar says.

6-minute or 15-minute increments: what each costs

The Georgia opinion describes lawyers rounding to units of anywhere from 6 to 15 minutes, and both rules above point them to 6. If you run a legal support firm, I’d use the same unit as the law firms you bill, because a law firm that rebills your time to its own client needs it in the unit its own invoices use.

For accounting and consulting work, the increment is a term of your engagement letter, so it’s yours to agree with the client. What it costs each side depends on how long your entries are. Here is the same month in both increments, under both rules.

The time worked was 11 hours, or $1,650. Rounded up in quarter hours, the client pays $1,275 more than that, and $945 more than it would in tenths. Rounded to the nearest quarter hour, the firm bills $525 less than the time worked, because every 4-minute entry rounds down to nothing.

The gap comes from the short entries. Rounded up, the six 50-minute sessions (5 hours of work) bill as 5.4 hours in tenths or 6 in quarter hours, while the thirty 4-minute entries (2 hours of work) bill as 3 hours in tenths or 7.5 in quarter hours. So a quarter hour changes the bill least where work comes in long sittings, such as a month-end close or a workshop day, and most where a day is made of calls and emails.

Record time so you rarely need the chart

The chart is needed when people note clock times or minutes and convert them later, and most of that conversion can be avoided.

Run a timer while you work. The timer does the subtraction, and the entry exists as soon as the work ends, while you still know what it was for. The U.S. Trustee’s guidelines above also ask for entries to be kept at the time of the work.

When you add time afterwards, type the duration in decimal hours. If your timesheet accepts 0.4 as readily as 0:24, you enter the figure that will be billed and have nothing to look up.

Then let the software apply the increment, and use one increment everywhere. A quarter-hour entry typed as 0.25 is 15 minutes, and a system set to round up in 6-minute steps turns it into 0.3.

How Timebun records and rounds time

In Timebun, the software we build for firms that sell their time, your team can run a timer or type a duration. The duration field reads 1.2, 1:12, 1h12m and 72m as the same hour and 12 minutes, so nobody converts before typing.

Rounding is one setting for the whole workspace, Round billable time up to, under Settings → Time tracking. The choices are no rounding (the default), 0.1 hours, 0.25 hours, 0.5 hours and 1 hour. When an entry is finished, Timebun rounds its billable time up to the next step. It works from the tracked time to the second, so on 6-minute steps a timer stopped at 6 minutes and 1 second is billed as 0.2.

The setting only rounds up, with no option to round to the nearest step. It also holds one increment per workspace, so it can’t round one client’s time in tenths and another’s in quarter hours.

Rounding never overwrites the time you tracked. Each entry keeps both figures, and clicking its time shows them as Tracked and Billed as. If you change the increment later, entries already finished keep the figure they had, and the new increment applies to time finished or corrected after the change. An Admin or the Owner can also set the billed hours by hand on an entry that hasn’t been invoiced, when the rounded figure isn’t what you want to charge.

The billed figure is the one that goes on the invoice and the one that comes off a client’s retainer or prepaid hours. Under 6-minute rounding, the month in the example above would take 13.2 hours from a block of hours for 11 hours of work. How to bill clients for hours covers retainers and prepaid blocks.

How durations are displayed is a separate setting: hours and minutes (2:15), which is the default, or decimal (2.25). Reports and invoices use decimal hours whichever you choose. An invoice line carries hours to two decimal places, so with rounding off, a 7-minute call is invoiced as 0.12 hours, the same figure as the minute-by-minute chart above.

Clients you invite to the client portal see the billed hours for each finished, billable entry on their Time page. The page shows hours and minutes, and its CSV export gives the same hours as decimals.

Frequently asked questions

How many minutes is 0.1 of an hour?

0.1 of an hour is 6 minutes, because an hour has ten tenths. On the same scale, 0.25 is 15 minutes and 0.5 is 30.

How do you convert minutes to billable hours?

Divide the minutes by 60, then round to your billing increment. Forty minutes is 0.67 hours, which is 0.7 in tenths and 0.75 in quarter hours when you round up.

How do you calculate billable hours for an invoice?

Round each entry to the increment in your engagement letter, add the rounded entries, and multiply by the hourly rate. Entries of 0.3, 0.7 and 1.2 hours make 2.2 hours, which is $396 at $180 an hour.

Why do lawyers bill in 6-minute increments?

Six minutes is a tenth of an hour, so every entry has one decimal place and multiplies by the rate without a conversion. Smaller steps also keep the bill closer to the time worked than quarter hours do, as the example above shows.

Is it better to round up or to the nearest increment?

Use the rule written in your engagement letter or in the client’s billing guidelines, and use it for every entry. Rounding up always bills at least the time worked, while rounding to the nearest can bill more or less and bills nothing for an entry shorter than half a step.

If you run a legal support firm that bills law firms by the hour, see how Timebun works for legal support firms.