Most freelancers under-invoice by 15–25%. Not because they're being generous — because they don't track time accurately. They estimate at the end of the week based on memory, then round down because they feel guilty about a long lunch. This free billable hours calculator removes the guilt and the math: you log each session as you go (or paste in a list at the end of the day), set the hourly rate per project, and it tells you exactly what to invoice.
It's deliberately not a "time tracker" with a timer button. Time-tracker apps with always-on timers create their own kind of guilt and end up unused. This is a calculator: you tell it what you did, it tells you what to charge.
What it does
- Multi-project. Add as many projects as you want, each with its own hourly rate (and currency, if you have international clients).
- Decimal or hours-and-minutes. Type "1h 45m" or "1.75" — both work. The calculator normalises everything to decimal hours for billing.
- Daily and weekly totals. Shows hours and amount, by project, by day, and across the week. This is the number you put on the invoice.
- CSV export. Click export and you get a clean spreadsheet you can paste into your invoice template or upload to your accounting tool.
- Effective hourly rate. Bonus metric: divides your total earned by total hours worked across all projects. If your blended rate is below what you should be charging, raise it.
Worked example: one freelance week
A designer bills two clients at different rates. Here is a real week, logged the way the calculator expects it:
| Day | Project | Logged | Decimal hours | Rate | Amount |
|---|---|---|---|---|---|
| Mon | Client A — brand refresh | 3h 15m | 3.25 | $95 | $308.75 |
| Tue | Client A — brand refresh | 2h 45m | 2.75 | $95 | $261.25 |
| Wed | Client B — website audit | 4h 30m | 4.50 | $70 | $315.00 |
| Thu | Client A — brand refresh | 1h 30m | 1.50 | $95 | $142.50 |
| Fri | Client B — website audit | 2h 00m | 2.00 | $70 | $140.00 |
| Total | 2 projects | 14h 00m | 14.00 | — | $1,167.50 |
Two numbers matter here. The invoice totals are $712.50 for Client A and $455.00 for Client B. And the effective hourly rate is $1,167.50 ÷ 14.00 = $83.39 — well below the $95 headline rate, because the cheaper client took a third of the week. That gap is the number most freelancers never calculate, and it is the argument for either raising Client B's rate or dropping them.
Rate targets at a glance
Work backwards from the salary you want, assuming roughly 1,000 billable hours a year (about 20 billable hours a week, allowing for admin, sales, and time off):
| Target salary | Base rate | With 40% overhead | Day rate (7 billable hours) |
|---|---|---|---|
| $60,000 | $60 | $84 | $588 |
| $80,000 | $80 | $112 | $784 |
| $100,000 | $100 | $140 | $980 |
| $150,000 | $150 | $210 | $1,470 |
If your effective rate from the calculator is below the "with overhead" column, you are funding your own taxes, software, and downtime out of pocket.
Why a calculator and not a tracker
Time trackers measure when you started and stopped. That's the wrong unit. Clients pay for output. If you spent 90 minutes in flow and produced what would normally take three hours, you should charge for three hours of value, not 90 minutes. The calculator lets you log "what you actually delivered" rather than "minutes the timer was on", which both protects your rate and stops you from over-billing for context-switching time you'd rather absorb.
Pairs with
- Meeting Cost Calculator — for showing clients what their "quick call" actually costs.
- Sunday Reset Checklist — for the weekly review where you log the hours you forgot during the week.
When you outgrow it
If you need persistent time tracking across weeks, automatic invoice generation, and integrations with Stripe or Xero, you need something like Harvest or LemTask's focus module, which tracks billable focus sessions automatically once you sign in. The free version of LemTask covers the same ground for individual freelancers.