Compare a one-off project fee with a monthly retainer over the same stretch of time. Enter the project fee and hours, the retainer fee and included hours, how many months to compare, and an optional overage rate for hours above the retainer. You will see each option's total and effective hourly rate. The comparison runs in your browser.
A project fee is one number for a defined scope. Its effective rate is that fee divided by the hours the project will take. A retainer is a monthly fee in exchange for a set number of hours, or a set range of work, each month. Over several months the retainer total is monthly fee × months, and the included hours are hours per month × months. The effective rate on the included hours is the monthly fee divided by the hours included that month.
If the client needs more hours than the retainer includes, those extra hours can be billed at an overage rate or absorbed unpaid. When they are billed, the retainer-side total is the retainer fees plus overage hours times the overage rate, and the effective rate uses all hours worked. When they are absorbed, the fee stays the same and is divided by the larger hour count, so the effective rate falls. The project side does not change with those extra retainer hours, because it is a separate arrangement for a separate scope.
The comparison is only valid if both options are meant to cover a similar kind of work over the months you enter. A retainer for ongoing support is not a like-for-like substitute for a one-off build with a clear end date. The calculator does not estimate how much work will actually arrive, and it is not a forecast of income. For a flat fee versus hourly billing on a single scope, use the flat fee vs hourly calculator. To turn a day rate into a project quote, use the day rate to project quote calculator.
With the default numbers, a $4,800 project estimated at 48 hours is $100 an hour, and a $2,000 retainer with 20 hours included is also $100 an hour on the included time. Over three months the retainer fees total $6,000 for 60 included hours. Four extra hours a month, billed at $100, add $1,200, for a $7,200 total over 72 hours — still $100 an hour. If those 12 extra hours are absorbed unpaid, the effective rate on the $6,000 retainer is $83.33 an hour.
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Put both options on the same span of months. The project side is the one-off fee and the hours that job will take. The retainer side is the monthly fee times the number of months, the hours included each month, and any overage hours billed at the overage rate you enter. The calculator then shows each option's total and its effective hourly rate.
If you enter extra hours above the retainer allowance and leave them unbilled, the retainer fee is spread over more hours and the effective rate falls. The result also shows the rate if those extra hours are billed at the overage rate.
This page does not choose for you. A retainer can be steadier for ongoing work; a project fee can be clearer for a defined deliverable. The numbers only compare money and hours at the figures you type. They are not a forecast of how much work the client will actually send.