FREE CONTRACTOR TOOL

Change Order Price Calculator

Enter the direct cost of a change and your target gross margin. This calculator returns the correct customer price using the margin formula, plus a warning about how much the common markup mistake costs you on the same change.

Built by a Tampa Bay pool project manager who has watched crews leak 10 points of margin on every change order.

Change order numbers

$
Labor (burdened), materials, subs, direct equipment or fuel for the change. Nothing else.
%
Default 40 percent. Match or exceed the margin on the base contract.
%
Optional. Defaults to your target. Shows what pricing with a naked markup would actually deliver.
Optional. Used in the copy-paste line item text.

Result

The markup shortcut leaks margin.
Copy-paste line item
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How to use this calculator

Enter the direct cost of the change first. Direct cost is labor at your burdened rate, materials at your delivered cost, sub balances for the change, and any equipment or fuel that only exists because of the change. Do not include a share of overhead. Overhead lives in your target margin, not in the direct cost line.

Target gross margin defaults to 40 percent. If your base contract is priced at 38 percent margin, do not price the change at 38. Price it at 40 or 42. Change orders carry more schedule risk and rework risk than the base scope because they were not planned. The margin should reflect that. If the base is at 45, hold change orders at 45.

The Markup percent field is there for one reason: to show you the money that would walk off the job if you priced the change with a naked cost-times-markup formula. Leave it at 40 (matching the default target) the first time you run the tool. The output will show that a 40 percent markup on a $1,000 cost only delivers 28.6 percent margin, not 40. That gap is the reason this calculator exists.

The Scope description field feeds the copy-paste line item at the bottom. Write it the way you want it to read on the change order document. Homeowners do not want to see line-item labor, materials, and markup broken out. They want a scope and a number. Give them that.

Hit Price the change order. Everything runs in your browser. Nothing you type leaves your device. Copy the line item, drop it in your change order document, get it signed before the crew starts the work.

Why the math matters

The math on a change order is short. There is one formula that gets you the margin you actually want:

Price = Cost divided by (1 minus target margin as decimal). So $1,000 cost at 40 percent margin equals $1,000 divided by 0.60, which is $1,666.67. That price delivers exactly 40 percent gross margin because ($1,666.67 minus $1,000) divided by $1,666.67 is 0.400.

The wrong formula is the one most contractors default to because it is what a calculator on a truck seat can do fast:

Wrong price = Cost times (1 plus markup percent). So $1,000 cost with a 40 percent markup equals $1,400. But the actual gross margin on that sale is ($1,400 minus $1,000) divided by $1,400, or 28.6 percent. You wanted 40. You got 28.6. That is 11.4 points of gross margin left on the truck.

Here is how the two formulas play out at common change order costs:

Direct cost Correct price (40% margin) Markup price (40% markup) Money left on truck Actual margin from markup
$500 $833.33 $700.00 $133.33 28.6%
$1,000 $1,666.67 $1,400.00 $266.67 28.6%
$2,500 $4,166.67 $3,500.00 $666.67 28.6%
$5,000 $8,333.33 $7,000.00 $1,333.33 28.6%

The actual margin from a 40 percent markup is always 28.6 percent, regardless of cost. It is a math constant, not a rounding error. To hit a true 40 percent margin with the markup formula, you would need a 66.7 percent markup. Nobody puts that number in their head. That is why the margin formula is the right formula for change orders and why this calculator only shows you the markup number for the purpose of confirming you should not use it.

The Field-Office Latency Gap

The Field-Office Latency Gap is the hours-not-minutes lag between a job-site event and when the office sees it. On change orders, the gap is where profit dies. The homeowner asks for extra work at 10am Tuesday. The crew scribbles the request on a jobsite napkin. The PM types it into a Word doc Thursday night. The customer sees a price on Friday afternoon. That is three days for a $2,000 change. In that window, the crew has often already done half the work, either free or at the wrong margin because nobody agreed on a price up front.

I watched this happen on a Land O' Lakes pool remodel in the summer of 2024. Homeowner asked for a paver deck extension on a Monday walk-through. The crew heard "sure, we can do that." The PM (me) heard about it Thursday. By then the crew had ordered the pavers, poured the extra concrete pad, and started laying. The invoice went out at a number the homeowner had never signed. She paid, grumbling. I made 22 percent margin on the change instead of the 40 I would have signed her up for on Tuesday morning. That is the Latency Gap costing 18 points on a $3,400 change, which is $612 in real money.

A phone-based change order flow closes the gap. Homeowner asks on the walk-through, PM opens the app, punches direct cost, target margin, and scope, and sends a signable change order in under two minutes. Homeowner signs on the driveway. Crew starts the work with a signed number. Nobody eats margin later. That is what Workhand's estimate and change order flow is built for.

Frequently asked questions

How do I price a change order in construction?
Take the direct cost of the change (labor, materials, subs, direct equipment), then divide it by (1 minus your target gross margin as a decimal). Example: a $1,000 direct cost with a 40 percent target margin prices at $1,000 divided by 0.60, which is $1,666.67. That is the margin formula, and it is the only formula that actually delivers the margin you targeted. Do not use the markup shortcut (cost times 1 plus markup) unless you have already recomputed the markup percent that corresponds to your target margin, which most contractors have not.
What is the difference between markup and margin on a change order?
Markup is applied to cost. Margin is measured against price. A 40 percent markup on a $1,000 cost gives a $1,400 price, and the actual margin on that sale is only 28.6 percent. To hit a real 40 percent margin, you need to divide cost by (1 minus 0.40), which is $1,666.67. Contractors who confuse the two lose about 8 to 12 points of margin on every change order they price the wrong way. On a $2,000 direct cost, that is $200 to $300 walking off the job every time a homeowner asks for an extra.
What is a fair markup for a change order?
The question itself is the trap. Do not think in markup, think in target margin, then let the formula give you the right price. Common target margins for change orders on residential remodel and pool work are 35 to 45 percent gross margin. That translates to markup percentages of 54 to 82 percent on cost, which is why the markup number scares contractors into pricing too low. Target margin on the change order should match or exceed target margin on the base contract. If anything, change orders should carry a slightly higher margin because they carry more schedule risk and rework risk.
Should I break out labor, materials, and markup on the change order line item?
For residential work, no. Homeowners see the material cost and immediately compare it to Home Depot, then argue the markup. Give a single lump-sum line item with a clear scope: "Change Order 3: Add pool light on north wall including trench, conduit, wiring, fixture, and trim. Total $1,667." You quoted a scope for a number. That is the deal. For commercial or public work you may be contractually required to itemize labor rate, material at cost, and a stated markup. In that case use the same margin formula on the total, then back into the itemized breakdown.
Do I need the homeowner to sign the change order before I do the work?
Yes, every time, no exceptions. A verbal is not a contract when the invoice arrives and the homeowner remembers the number differently. Get the change order signed (paper, e-sign, text message with a picture of the signed page, whatever fits the state and the customer) before the crew touches the change. The number one profit leak on small jobs is not underpricing, it is doing $2,000 in change work with no signed authorization and then eating half of it in the collections fight. Workhand has an in-app estimates and change orders feature with e-signature for this reason.
Is this calculator free to use?
Yes. No signup, no email gate, no watermark. Everything runs in your browser. Nothing you enter is sent to a server. If you want the same math built into an estimate and change order flow with e-signature and deposit collection, Workhand has a free plan for one active job.

Want signed change orders from the driveway?

Workhand does estimates and change orders on your phone. Punch cost, target margin, scope. Send the change order to the homeowner. They sign on the driveway. Deposit hits your Stripe account before the crew starts. Free plan for one active job, no credit card.

See how estimates and change orders work or Get Workhand free

Related reading: How to follow up on a construction estimate and How to calculate profit per job. Also useful: the job profit margin calculator for the base contract.

Built and operated by Andrew Bernardo, project manager at a Tampa Bay pool builder, at Innovative Ops LLC in Wesley Chapel, Florida.