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What you've already put in determines how much each following installment is worth

After this lesson, you'll know how to calculate what percentage of the price each mid-project installment should be based on what that phase actually costs, not split evenly.

By Yodai · Published on September 6, 2026 · Updated on October 12, 2026

When you bill a big job in stages, the first thing to decide is how much you ask for before you touch the first piece of material. Then comes the question almost nobody gets right: how much each stage after that first payment is worth.

The quick answer, the one almost everyone gives, is to divide what's left by the number of installments remaining. If there are three, a third each. It sounds fair, it's easy to explain in a quote, and it's a mistake that costs you dearly halfway through the job.

One installment isn't worth the same as another because they don't cost the same. One takes up half your hours and almost no materials. Another forces you to buy expensive supplies before that phase even starts. If you charge the same for both, you work at a loss on the expensive one until the next payment comes in, and you cover that gap yourself, out of pocket, the whole time.

Each installment is worth what it costs, not whose turn it is

Take the whole job and break it into phases, not calendar dates. In a kitchen remodel, for example, there's a demolition and plumbing/electrical phase, a tiling and finishes phase, and a final handoff with touch-ups and inspection. Three phases, and each one carries a different weight in the price.

The demolition and installation phase takes the toughest hours and the priciest trades: plumber, electrician, labor that can't be pushed back or spread across several separate days. The finishes phase takes fewer hours but more visible material, the kind the customer sees and touches at the end. The final handoff is mostly inspection, touch-ups, and the warranty you sign off on when you close out the job. If you assign the same percentage to all three phases, the most expensive one stays underpaid for weeks, and the cheapest one hands you a cushion you don't need right there.

The rule is simple to apply even if it's not simple to calculate down to the penny: add up what each phase costs you in committed materials and hours of work, and that's the weight you give it in the final price. You don't need a detailed cost spreadsheet, an honest estimate is enough.

If your business doesn't buy materials, time sets the weight

Not every business buys materials before a phase. If you sell web design, a training plan, or a marketing campaign, what matters isn't what you buy, it's the time each phase takes and the business you turn down while you're doing it.

For a website, the layout and content phase takes more hours than the final adjustments phase, even if both take up a similar number of days on the calendar. That installment carries more weight even though you haven't bought anything, because that's where you put in the days you couldn't spend on another client. Materials get replaced by hours, but the rule for weighing the installment stays exactly the same.

How to weigh a phase without knowing the exact cost

You'll almost never know the exact cost of each phase before the job starts. That doesn't change the rule: you need a rough yardstick, not equal shares split out of convenience.

Ask two questions per phase: how many hours of your time or your team's time go into it, and how much material you have to pay for before that phase starts. Add them up and compare against the other phases. You don't need the exact number, you need the order: which one weighs more, which one weighs less, and by how much.

If you're torn between two weights for the same phase, round up the one with more risk for you, not the one with more visible work. Risk is what you've already put out of your own pocket and haven't been paid back for yet.

What to tell the customer when one installment weighs more than the others

If the customer asks why the second installment is 40% instead of a third, the answer isn't about pricing, it's about the work. Tell them what happens in that phase: which trades are involved, what material gets paid for up front, how many days are packed into it.

You don't need to show your margin or your internal numbers. Just naming what happens in that phase is enough for the percentage to make sense on its own. A customer who reads "plumbing and electrical" understands why that stage carries more weight than the final walkthrough, without you having to justify it twice. And if you need to, show them the whole weight table: seeing all four stages side by side explains more than any argument would.

With this, you've got the price split into installments that weigh what they actually cost, not whose turn it is next. What's left is putting a date on each one and deciding what happens if an installment doesn't come through, and that's what's next.

You already know how to work out the weight of each stage. All of that (stages, amounts, and which milestone triggers each payment) needs to be written down and signed before the first hour of work, not negotiated stage by stage as you go.