Billable Hours Calculator Guide for Freelancers

What counts as billable hours?

Billable hours are the time you charge to a client or project.

Depending on the agreement, this could include:

• producing the agreed work
• project-specific research
• client calls
• meetings
• agreed revisions
• implementation
• testing
• project-specific preparation
• project handover

Other working time may be non-billable. Examples might include:

• bookkeeping
• marketing
• finding new clients
• general business administration
• training
• preparing your own accounts
• unpaid breaks

Whether a particular activity is billable depends on the agreement with the client.

The important thing is to separate client billable time from the rest of the time spent running the business.

Billable hours vs total working hours

Working for eight hours does not automatically mean you have eight billable hours.

Total time: 8 hours. Billable client time:

4h30m + 45m + 1h15m = 6h30m

Decimal equivalent: 6.50 hours

So the invoice calculation should normally begin with 6.50 billable hours rather than the full eight-hour day.

How to calculate one billable work session

For a single continuous work session, use:

Finish time − start time − non-billable breaks = billable time

• Start: 09:10
• Finish: 12:25
• Elapsed time: 3h15m
• Non-billable break: 15m
• Billable time: 3h00m

If the whole remaining period relates to the client project, the billable session is 3.00 hours.

For more detail on calculating elapsed time, see How to Calculate Hours Between Two Times.

How to add multiple billable tasks

Freelance work often happens in several separate blocks rather than one continuous session.

That gives 5h40m of billable time to use for the next stage of the calculation.

Convert billable hours and minutes to decimal hours

If the invoice calculation uses an hourly rate, converting the final time into decimal hours makes multiplication straightforward.

The formula is: Minutes ÷ 60 = decimal part of an hour

Common examples:

A common mistake is to write 2.45 hours when you mean 2h45m.

45 ÷ 60 = 0.75

So 2h45m = 2.75 hours, not 2.45.

How to calculate the invoice amount

Once you know the billable decimal hours:

Billable hours × hourly rate = labour charge

For example, with 5h40m of billable time (5.6667 hours) at £50 per hour:

5.6667 × £50 = £283.33

So the labour amount is approximately £283.33.

If your agreement requires a particular rounding method, apply that consistently before calculating the final charge.

Multiple clients with different hourly rates

Different clients or projects may have different rates. In that case, calculate them separately.

Client A

Billable time 3h at £40/hour:

3 × £40 = £120

Client B

Billable time 2h30m, which is 2.50 hours, at £60/hour:

2.50 × £60 = £150

Combined billable time 5h30m, combined labour revenue £270.

Do not combine the hours first if different parts of the work use different rates.

Weekly, monthly or project billing totals

You may want to total billable time across a longer billing period.

• Week 1: 8h15m
• Week 2: 6h45m
• Week 3: 9h30m

8 + 6 + 9 = 23h

15 + 45 + 30 = 90 minutes = 1h30m

Total: 24h30m, or 24.50 hours

At £45/hour the labour charge is:

24.50 × £45 = £1,102.50

How breaks and interruptions affect billable time

Not every minute between starting and finishing a work session necessarily belongs on the client invoice.

For example, you may need to remove:

• lunch
• personal breaks
• unrelated phone calls
• internal admin
• work for another client
• unrelated interruptions

But a client-related call or project-specific research session may still be part of the billable work.

The safest approach is to track the task that was actually being worked on rather than assuming the entire period is billable.

Should freelancers round billable time?

Some freelancers charge exact elapsed time. Others use agreed billing increments such as:

• 6 minutes
• 10 minutes
• 15 minutes
• 30 minutes

The arrangement may also specify whether a partial increment is rounded upward, downward or to the nearest increment.

For example, 20 minutes is exactly 0.3333 hours. But under a billing arrangement that rounds up to 6-minute units, it could be recorded as 24 minutes, or 0.4 hours.

The billing method should come from the agreed way of charging for the work rather than being applied arbitrarily after the work is complete.

For more detail, see 6-Minute Billing Increments Explained.

What if I charge a fixed project fee?

Not all freelance work is charged by the hour.

Suppose you charge £600 for a fixed-price project and spend 12 hours completing it.

£600 ÷ 12 = £50/hour

The invoice may still be £600, because that was the agreed project price.

But tracking the hours can help you understand:

• whether the project was profitable
• whether your estimate was realistic
• whether similar future projects should cost more
• how much time different stages actually take

What is billable utilisation?

Billable utilisation compares client-billable time with total working time.

The formula is: Billable hours ÷ total working hours × 100

For example, with 26h of billable client time and 40h of total business working time:

26 ÷ 40 × 100 = 65%

This can be useful for business planning, but it does not directly determine what goes on an individual client invoice.

Track time as you work

Accurate billable hours are easier to calculate when the underlying time record is accurate.

A simple workflow is:

1. record the client or project
2. record the task
3. record when the work starts
4. record when it finishes
5. note any breaks or interruptions
6. mark whether the activity is billable
7. total the entries later

This is usually more reliable than trying to reconstruct an entire week’s work from memory.

From tracked time to invoice

A simple freelance billing workflow is:

1. collect the client time entries
2. remove non-billable time
3. total the billable hours and minutes
4. convert the final total into decimal hours
5. apply any agreed billing increment
6. multiply the hours by the correct client rate
7. keep different rates separate
8. transfer the final time and charge to the invoice

For example, tracked billable time of 7h45m is 7.75 hours. At £55/hour:

7.75 × £55 = £426.25

Common freelancer billing mistakes

Treating every working hour as billable

Running a freelance business also involves admin, marketing and other non-client work.

Forgetting breaks

A break should not automatically become client billable time.

Entering 2h45m as 2.45 hours

The correct decimal is 2.75 hours.

Mixing client work with internal admin

Keep project-specific work separate from time spent running your own business.

Applying the wrong hourly rate

Different clients or projects may have different rates.

Combining hours before checking the rate

Calculate each rate category separately before adding the charges together.

Using inconsistent rounding

If work is billed in increments, use the agreed method consistently.

Reconstructing time from memory

Small tasks are easy to forget or overestimate later.

Calculating the invoice before checking the time entries

The final charge is only as reliable as the time record behind it.