How big should the risk buffer on a fixed-price quote be?

Tie it to how much you know: 10-15% for a written spec, work you have done before and a single decision-maker; 25-35% when the brief is loose, the deadline is tight or several stakeholders must approve. If your own recorded hours consistently run 20% over estimate, that number is your floor.

Should I show the client the buffer as a separate line?

Usually not as 'buffer'. Present one fee for a defined scope, and keep the internal breakdown for your own records. What does belong in the document is the number of revision rounds included and the hourly rate for anything beyond them.

Is fixed-price or hourly better for freelance work?

Fixed price rewards speed and experience but punishes vague scope, since every extra hour is unpaid. Hourly protects you when requirements are still moving. A common compromise is a fixed price for a clearly specified phase one, then hourly for follow-on work.

What do I do when a client asks me to cut the quote?

Cut the scope rather than the rate. Removing a revision round, a deliverable or a platform keeps the price per hour intact and makes the trade explicit, whereas discounting the same work resets the client's expectation for every future project.

Do revision rounds need to be paid separately?

Only when they exceed the number agreed. The hours for the included rounds should already sit inside the quoted fee, which is why this calculator adds them to estimated hours before applying the rate.

Project quote calculator

Turning an hourly rate into a fixed project price is where most independent workers lose money, because a quote is a promise about hours that have not happened yet. The arithmetic itself is simple — estimated hours, revision rounds and a risk buffer multiplied by your rate — but each of those three inputs hides a judgement call, and the buffer is the only one that protects you when the estimate turns out optimistic.

What a fixed price is really selling

When a client asks for a fixed price rather than an hourly arrangement, they are buying certainty and transferring schedule risk onto you. That transfer has a market value, and pricing a fixed-scope project at exactly hours times rate hands the certainty over for free.

Every hour spent past the estimate is unpaid at a fixed price, so the effective rate falls with each overrun. A 40-hour estimate quoted at 100 an hour yields 4,000; if delivery actually takes 52 hours, the realised rate is about 76.92 an hour, a 23% pay cut that the client never sees and never agreed to.

The buffer percentage in this calculator is the price of that risk transfer. Treat it as a deliberate line item rather than padding, and it becomes easy to defend in a negotiation: a shorter deadline, a vaguer brief or a committee of approvers all justify a larger one.

Three quotes built from the same rate

A brand identity project estimated at 40 hours, with two revision rounds costing 4 hours each, comes to 48 hours. At a rate of 110 and a 15% buffer, the quote is 48 × 110 = 5,280, plus 792 of buffer, for 6,072 — a figure most people would round to 6,000 or 6,100 when presenting it.

A tightly specified integration job estimated at 20 hours with a single 2-hour revision round and a small 10% buffer, billed at 140, comes to 22 hours, 3,080 of base fee and 308 of buffer: 3,388. The narrow buffer reflects a written spec and one decision-maker.

A vague 'website refresh' with no wireframes, an estimate of 60 hours, three 6-hour revision rounds and a 30% buffer at 95 an hour reaches 78 hours, 7,410 of base fee and 2,223 of buffer, for 9,633. If that number feels high, the honest response is usually to narrow the scope rather than shrink the buffer.

Estimating hours you have not worked yet

Break the project into tasks small enough that you have done something comparable before, estimate each one, then add the pieces. Estimates made at the level of a whole project tend to compress; estimates made per task expose the setup, review and handover work that a single top-level guess quietly omits.

Include the unglamorous hours: kick-off calls, feedback meetings, asset collection, exports, deployment and the final round of small corrections. On short projects this administrative tail is routinely a fifth of total time, and it is the part clients least expect to see itemised.

Record actual hours against every quote you issue, even when you are paid a fixed fee. After five or six projects the ratio of actual to estimated hours becomes a personal multiplier that is far more accurate than any generic rule of thumb about padding estimates.

Scope, revisions and payment terms in the contract

A revision round needs a written definition, otherwise it becomes a rolling conversation. Naming the number of rounds, the window for feedback, and what counts as a new request rather than a revision converts the revision-hours input in this calculator into an enforceable limit.

State an hourly rate for out-of-scope work in the same document as the fixed price. Without it, the only options when scope grows are absorbing the cost or renegotiating from scratch, and neither is comfortable mid-project.

Fixed-price work concentrates cash-flow risk at delivery, so staged payments matter more here than on hourly engagements. A deposit before work starts and a milestone payment partway through are standard practice for independent contractors, and the US Small Business Administration's guidance on managing business finances treats invoicing terms as a core cash-flow control rather than an afterthought.

Jurisdiction shapes the paperwork around the price. In the UK, consumer clients have statutory cancellation rights on contracts agreed at a distance, and VAT-registered freelancers must add VAT on top of the quoted figure; in the US, some states apply sales tax to specific categories of service work. The quote this tool produces is the pre-tax fee in all cases.

Frequently asked questions

How big should the risk buffer on a fixed-price quote be?: Tie it to how much you know: 10-15% for a written spec, work you have done before and a single decision-maker; 25-35% when the brief is loose, the deadline is tight or several stakeholders must approve. If your own recorded hours consistently run 20% over estimate, that number is your floor.
Should I show the client the buffer as a separate line?: Usually not as 'buffer'. Present one fee for a defined scope, and keep the internal breakdown for your own records. What does belong in the document is the number of revision rounds included and the hourly rate for anything beyond them.
Is fixed-price or hourly better for freelance work?: Fixed price rewards speed and experience but punishes vague scope, since every extra hour is unpaid. Hourly protects you when requirements are still moving. A common compromise is a fixed price for a clearly specified phase one, then hourly for follow-on work.
What do I do when a client asks me to cut the quote?: Cut the scope rather than the rate. Removing a revision round, a deliverable or a platform keeps the price per hour intact and makes the trade explicit, whereas discounting the same work resets the client's expectation for every future project.
Do revision rounds need to be paid separately?: Only when they exceed the number agreed. The hours for the included rounds should already sit inside the quoted fee, which is why this calculator adds them to estimated hours before applying the rate.

Sources

U.S. Small Business Administration — Manage your finances — Federal small-business guidance describing invoicing, payment terms and cash-flow planning as core operating controls for very small firms and sole proprietors.
GOV.UK — VAT registration — Sets out the UK VAT registration threshold and the obligation to charge VAT on top of quoted fees once a business is registered.