Billing in 6-minute increments: rounding rules for billable time

Hourly billing needs a unit. Lawyers and accountants settled on a tenth of an hour decades ago, many creative freelancers use quarter hours, and timer apps make exact time easy. This post, part of the time and projects hub, puts numbers on each choice. For the tracking routine itself, start with how to track billable hours.

Minutes to tenths of an hour

If you round to the nearest tenth instead, the breakpoints sit halfway: 1 to 2 minutes rounds to 0.0, 3 to 8 minutes to 0.1, 9 to 14 minutes to 0.2, and so on. Exact decimal hours are simpler still: divide minutes by 60, so 38 minutes is 0.63 hours.

Rounding policies compared on one day of work

The policy matters most when a day is made of many short entries. Here are six real-looking entries from one client day: a 4-minute email, an 11-minute call, 38 minutes of drafting, 52 minutes of revisions, a 7-minute email and 23 minutes of review. Exact time is 135 minutes, or 2.25 hours.

Rounding up on every entry adds about half an increment per entry on average: 3 minutes per entry in tenths, 7.5 minutes in quarter hours. On a day with six entries that is 18 or 45 extra minutes. Rounding to the nearest increment pushes some entries up and some down, so a month of it lands close to exact time.

Is rounding up billable time fair?

Clients accept a minimum charge for a short task if they agreed to it in advance, and a tenth of an hour for reading and answering an email is a common example. What they don't accept is discovering it on the invoice. Lawyers' ethics opinions draw the line clearly: ABA Formal Opinion 93-379, quoted in D.C. Bar Opinion 267, says an hourly biller is never justified in charging for hours not actually expended, and the North Carolina State Bar treats billing time not actually spent as time padding. A disclosed minimum increment is a pricing term; silent rounding up across every entry is closer to padding.

Employee timekeeping offers another reference. Federal wage rules accept time clocks that round start and stop times to the nearest 5 minutes, tenth or quarter hour, but only if the practice doesn't, over time, fail to pay employees for all the time they worked (29 CFR 785.48). Freelancers aren't covered by that rule, yet the same test works for a client relationship: over a month, does your rounding average out?

Rounding policy wording for your contract

Time billing. Hourly work is billed at $[rate] per hour.

Option A (exact): Time is recorded with a timer and billed to the nearest 0.01 hour.

Option B (increments): Time is recorded in increments of [6 / 15] minutes. Each task is rounded [to the nearest increment / up to the next increment], with a minimum charge of [0.1 / 0.25] hour per task.

Timesheets showing the date, task and time for each entry are sent with every invoice. Questions about an entry must be raised within [10] days of the invoice date.

Send the timesheet with the invoice so the rule is visible in practice; the freelance timesheet template has a column for decimal hours, and the time card calculator converts start and end times into decimals.

How SoloWOS handles rounding

SoloWOS doesn't round to 6 or 15 minutes. When you track billable hours, entries are stored to the second. On an invoice, Add unbilled time groups the project's billable entries by description and converts each group to hours to the nearest 0.01 hour (36 seconds), rounding half up. If your contract uses 6- or 15-minute increments, edit the quantity on the invoice line before you send it; the line still links to the same time entries, so they won't be billed twice.