How to Calculate Billable Hours: Formula & Examples
To calculate billable hours, add up the time you spent on work a client agreed to pay for, then multiply by your hourly rate. The math is trivial. The hard part (and where most freelancers lose money) is capturing all the billable time in the first place, and drawing a consistent line between what's billable and what isn't.
What is the billable hours formula?
Billable amount = billable hours × hourly rate
And to get billable hours for a period:
Billable hours = sum of all time entries marked billable
A worked example for one week on one client:
| Task | Time | Billable? |
|---|---|---|
| Design work | 6h 30m | Yes |
| Client call | 45m | Yes |
| Revisions | 1h 15m | Yes |
| Internal admin | 40m | No |
| Proposal for a new lead | 30m | No |
| Billable total | 8h 30m |
At a $90/hour rate: 8.5 × $90 = $765 billable for the week. The 70 minutes of admin and sales are real work, but they're non-billable. They don't go on this client's invoice. Run your own week through the billable hours calculator to total it and apply a billing increment.
Step by step
- Track every task with its duration. You can't sum what you didn't capture. This is the step that quietly breaks. See below.
- Mark each entry billable or non-billable. Decide once, per project or task type, so it's consistent.
- Convert minutes to decimal hours. 8h 30m = 8.5 hours. (Minutes ÷ 60: 30 ÷ 60 = 0.5.) Most invoices and rate math use decimal hours, and the hours to decimal calculator converts a whole column in one place.
- Apply the rate. Multiply billable decimal hours by your rate. Use different rates per client or project if you have them.
- Round consistently, and document it. If you round to the nearest 15 minutes, do it the same way every time and tell clients up front. Inconsistent rounding is both a trust problem and a source of lost income. A freelance timesheet template with fixed columns makes that consistency easier to hold.
What does a billable month look like?
A single week is easy to eyeball. A month is where the real number lives, because it blends your strong weeks with your admin-heavy ones. Here is one freelancer's month across two clients at two rates:
| Week | Client | Billable hours | Rate | Revenue |
|---|---|---|---|---|
| Week 1 | Acme | 18 | $90 | $1,620 |
| Week 1 | Bell | 9 | $110 | $990 |
| Week 2 | Acme | 22 | $90 | $1,980 |
| Week 2 | Bell | 6 | $110 | $660 |
| Week 3 | Acme | 15 | $90 | $1,350 |
| Week 3 | Bell | 12 | $110 | $1,320 |
| Week 4 | Acme | 20 | $90 | $1,800 |
| Week 4 | Bell | 8 | $110 | $880 |
| Month total | 110 | $10,600 |
Two things fall out of a month like this. First, the monthly billable total (here 110 hours for $10,600) is the figure to compare against an income goal, not a single strong week. Second, the rate blend matters: Bell pays more per hour, so shifting hours toward Bell lifts revenue without changing either rate. Total your own month the same way in the billable hours calculator, and convert any h:mm entries with the hours to decimal calculator before you multiply.
How many billable hours are in a month?
There is no fixed answer, because billable hours are a share of the hours you work, not the days on the calendar. A common planning range is 20 to 30 billable hours a week, which lands around 80 to 130 billable hours a month once you subtract sales, admin, and the weeks that run light. The 110-hour month above is a realistic, sustainable load rather than a stretch. If your monthly total sits far below that, the gap is usually non-billable time or unbilled work that leaked away, not a shortage of hours at the desk. Your real number is whatever a few tracked months average out to.
How rounding changes the monthly total
Billing increments compound over a month. If you round every entry up to the nearest 6 minutes, a scatter of short tasks each gains a little, and across 110 hours of entries that adds up. Round to the nearest unit rather than always up if you want the fairest total, and apply the same increment to every entry so the month reconciles. The safest habit is to bill in decimal hours to the second where your contract allows it, and reserve rounding for the clients who require a fixed increment. Whatever you pick, document it once and hold to it, because an inconsistent rule is both a trust problem and a slow leak. A printable billing increment chart shows what each minute bills under 6, 10, 15 and 30 minute rounding, so you can compare rules before you commit to one.
Which mistakes cost you the most money?
- Reconstructing from memory. Adding up the week on invoice day means you only remember the big blocks. The small, frequent tasks (the ones that sum to real money) get dropped.
- Forgetting to start a timer. Time worked before the timer started is simply gone. Across a month this is often the single biggest leak.
- Always rounding down "to be safe." Generous to the client, expensive for you. Round to the nearest unit, not always downward.
- Mixing billable and non-billable. If you don't separate them, you either over-bill (and erode trust) or under-bill (and lose income). Knowing the split is also how you measure billable utilization.
- Not converting to decimal. Multiplying $90 by "1:20" instead of 1.33 quietly mangles the total. Convert h:mm to decimal first, then apply the rate.
- Judging income on one week. A light week after a heavy one looks like a problem that is not there. Total the month before you draw conclusions about a client or your rate.
Let the calculation do itself
The reliable way to calculate billable hours is to never assemble them by hand. If your time is captured automatically and each entry already carries a billable flag, the total is just a sum the software runs for you, for any client and any date range. Six billable hours trackers compared sorts the tools by whether they actually do that.
Automatic time tracking records your working day in the background; billable status is inherited from the project; and the billable total is live, ready to drop straight onto an invoice. That removes both error-prone steps (the capturing and the summing) at once.
BillNotch does exactly this: it tracks automatically, sums your billable total to the second, and generates a PDF invoice from it. See how to track billable hours accurately, or learn what counts as billable. Lawyers converting minutes to tenths on each matter can see that workflow in time tracking software for lawyers.
Frequently asked questions
How do you calculate billable hours?
Total the time you spent on client work that your agreement lets you charge for, then convert it to the unit you bill in. Add each task's duration across the period, keep billable and non-billable separate, and express the billable total in decimal hours or your rounding increment. Multiply by your rate to get the amount due.
How many billable hours are in a month?
That depends on how much of your worked time is billable, not on the calendar. A 40-hour week is about 160 worked hours a month, but realistic billable time is lower once selling, admin, and unpaid client work come out. For many freelancers the billable figure lands closer to 90 to 125 hours a month.
How do you convert minutes to decimal hours?
Divide the minutes by 60. Fifteen minutes is 0.25 hours, 30 is 0.5, and 45 is 0.75; six minutes is 0.1, which is why legal and consulting work often bills in tenths of an hour. Keeping time in decimals makes the rate math one multiplication instead of juggling hours and minutes.
Should I round billable hours?
Only if your contract or client expects it, and then consistently. Rounding every task up to the nearest 15 minutes adds up in your favor but can read as padding; rounding down quietly gives work away. Whichever convention you use, apply it the same way everywhere and state it, so the total is one you can defend.