How do I calculate a revised contract price with change orders?

Add every signed change order to the original contract. Additions increase it and credits reduce it. Leave out anything that has been priced but not signed, because an unagreed price is not part of the contract yet and billing against it is how a job ends up in an argument.

Does a change order have to be signed before the work starts?

For a covered California home improvement contract, yes. Business and Professions Code section 7159, which is published at leginfo.legislature.ca.gov, says a change to the contract must be in writing and signed by the parties before the changed work begins. Other contracts follow their own terms, so read yours and check with your attorney.

What is the difference between a change order and a new contract?

A change order changes a contract that already exists. It describes the added or removed work, the amount added to or subtracted from the price, and any effect on the schedule, and it becomes part of the original agreement. A new contract replaces the original, and most jobs never need one.

What percentage of a contract can be a change order?

There is no industry number, and anyone quoting one is guessing about your contract. What matters is the threshold in YOUR agreement, which is why the calculator takes it as an input and ships at 10 percent. Set it to whatever your own contract says, then watch it on each job.

Why is the unagreed work kept out of the revised contract total?

Because until the customer signs, nobody has agreed to pay for it. Adding it into the contract total flatters the job and hides the risk. Keeping it in its own figure shows you exactly how much priced work is sitting there unsigned, which is usually the number a contractor most needs to see.

Is retainage withheld from change orders too?

Usually yes. A signed change order becomes part of the contract, so the same retainage percentage applies to the higher revised total unless the change order says otherwise. That is why the last invoice on a job with a lot of changes is often smaller than the contractor expected.

Free Change Order Calculator

Original contract amount

The signed number, before any changes. What the customer agreed to at the start.

Change orders signed so far

Every change you and the customer both signed, added up. This is the only money that counts toward the revised contract total.

Signed changes add work or take it away?

A change order can take work away as well as add it. Pick credit back and the revised contract drops by the amount.

Priced, not signed yet

Extra work you have priced and talked about, with nothing on paper. Leave it at 0 if there is none. Get it in writing before the crew starts, and it moves into the field above.

That unagreed work adds or takes away?

A change order can take work away as well as add it. Pick credit back and the revised contract drops by the amount.

Billed to date

What you have already invoiced on this job, including progress payments. What is left to bill is the revised contract minus this.

Retainage withheld, %

The share the customer holds back until the job is done. Leave it at 0 if this job has none. Retainage is withheld against the revised contract, so a signed change gets held back too.

Your signature threshold, %

The share of the original contract that needs a fresh signature before the change is agreed. Ten percent is the common contract term. Set it to whatever your own agreement says, because this number is yours and not ours.

$1,850 of work is priced but not signed. It is not in the revised contract below, because nobody has agreed to pay for it yet. Get it in writing before the crew starts.

Revised contract total

$52,700

Original contract plus signed changes. Nothing unagreed is in here.

Signed changes are

8.7%

Sign the $1,850 you priced and the contract total goes to $54,550, or 12.5% of the original.

Your signature line sits at

$4,850

$650 of change left before you hit your own 10.0% line

Still to bill

$30,700

41.7% of the revised contract is already billed

Held back as retainage

$5,270

a share of the revised total, not just the original contract

Paid once retainage releases

$47,430

If the unagreed work gets signed

$54,550

12.5% of the original contract. Still not in the revised total above.

Change against the original contract

Agreed 8.7%Priced, not agreed 3.8%

The Revised Contract Price

The revised contract price is the original contract plus every change order that has been signed, and nothing else. Not the change you priced on Tuesday. Not the one the customer said yes to in the driveway. The signed ones.

That is the rule the calculator applies, and it will not let you talk it out of the rule. Put a number in the unagreed field and it appears in its own tile with its own label, while the revised total above it does not move. It moves the day the signature lands, and until then it is a price, not a receivable.

A change order can also take work off the job. Pick credit back and the revised total drops, which is the honest answer when the owner removes a scope item. If you want the paperwork half of this, the free change order template has the signable form.

THE REVISED CONTRACT

$52,700

Original $48,500

Signed $4,200

Signed changes are 8.7% of the original contract. That is the whole of the increase, and it is the only increase you can bill against.

AND THE PART NOBODY HAS AGREED TO

$1,850

Priced, quoted, talked about, unsigned. It sits outside the revised contract and outside every figure on this page until a signature lands on it.

The number on this page is the one you can bill against.

A calculator tells you the revised total once, with the numbers you remembered. SiteOps builds the change order against the contract, gets the customer signature, and moves the revised contract price the moment that signature lands. The signed copy stays on the job record.

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See how SiteOps handles contracts and change orders

Sign It Before the Crew Starts

The expensive version of a change order is the one you write after the work is done. By then the extra is finished, the customer is comparing your invoice to a number they agreed to months ago, and what should have been a two minute signature becomes a conversation about what was included.

So the sequence matters more than the form. Notice the extra. Price it. Get the signature. Then start. A change order signed first is part of the contract and the crew hours on it are earning. Signed last, it is a request.

SIGNED FIRST

Notice the extra

Price it

SIGN IT

Do the work

SIGNED LAST

Notice the extra

Do the work

Price it

Ask for a signature

Same four steps, same job, same price. One of them ends with money in the account and the other one ends with a phone call.

The Priced But Unagreed Column

The unagreed figure on this page is not a nag. It is the number that tells you how much work is already at risk on this job, and it is the same figure the calculator refuses to add to the revised contract until somebody signs.

Keep that number at zero and the job has no argument in it. Watch it climb and you know what the next hour of your week is for.

CHANGE AS A SHARE OF THE CONTRACT

12.5%

SIGNED

8.7%

YOUR LINE

10.0%

$4,850 on this contract

ROOM LEFT

1.3%

The dashed line is yours to set. Ten percent is the common contract term and it is the default here, but the number that matters is the one in your own agreement.

What SiteOps Does With It

The calculator prices one change order. The contract and change order tools in SiteOps build it against the contract. It carries the scope, the amount, and the effect on the completion date. The customer signs it in SiteOps, and the signed copy lands on the job record.

The revised contract price in the product is derived the same way this page derives it, the original plus the signed change orders, so nobody hand-edits the original to make the paperwork match. Invoices bill against that revised price, and the change counts as revenue in the daily profit and loss for the job. The crew hours on the extra land on the same job through GPS-verified clock-ins.

ONE JOB, AND THE NUMBERS THAT MOVE TOGETHER

Original contract: $48,500
Signed change orders: + $4,200
Priced, not signed: $1,850 held out
Revised contract price: $52,700
Billed to date: $22,000 (41.7%)
Held as retainage: $5,270
Still to bill: $30,700

The revised contract price is worked out, never typed in. Add a signed change order and it moves. Add an unsigned one and it does not.

Want the signable page instead of the math?

The free one-page change order template has the scope, the amount, the revised contract price, the schedule effect, and the two signature lines. Drop your email and the PDF opens right away.

Frequently asked questions

How do I calculate a revised contract price with change orders?: Add every signed change order to the original contract. Additions increase it and credits reduce it. Leave out anything that has been priced but not signed, because an unagreed price is not part of the contract yet and billing against it is how a job ends up in an argument.
Does a change order have to be signed before the work starts?: For a covered California home improvement contract, yes. Business and Professions Code section 7159, which is published at leginfo.legislature.ca.gov, says a change to the contract must be in writing and signed by the parties before the changed work begins. Other contracts follow their own terms, so read yours and check with your attorney.
What is the difference between a change order and a new contract?: A change order changes a contract that already exists. It describes the added or removed work, the amount added to or subtracted from the price, and any effect on the schedule, and it becomes part of the original agreement. A new contract replaces the original, and most jobs never need one.
What percentage of a contract can be a change order?: There is no industry number, and anyone quoting one is guessing about your contract. What matters is the threshold in YOUR agreement, which is why the calculator takes it as an input and ships at 10 percent. Set it to whatever your own contract says, then watch it on each job.
Why is the unagreed work kept out of the revised contract total?: Because until the customer signs, nobody has agreed to pay for it. Adding it into the contract total flatters the job and hides the risk. Keeping it in its own figure shows you exactly how much priced work is sitting there unsigned, which is usually the number a contractor most needs to see.
Is retainage withheld from change orders too?: Usually yes. A signed change order becomes part of the contract, so the same retainage percentage applies to the higher revised total unless the change order says otherwise. That is why the last invoice on a job with a lot of changes is often smaller than the contractor expected.

This calculator and everything on this page are general information for contractors, not accounting, tax, or legal advice. Contract requirements, change order thresholds, and retainage rules differ by state, by owner, and by agreement, and a web page does not know yours. The defaults are editable examples, not industry benchmarks. Run your own contract past your attorney and your books past your CPA before you change how you price or bill work.

General information, not legal advice. Laws and exceptions change. Check the current California statute, CSLB guidance, and your attorney before relying on this.

Signed changes, on the job that earned them.

You just worked out one revised contract by hand. SiteOps keeps the whole job on one record. The contract, every signed change order, GPS-verified crew time, receipts with a job name, and a daily profit and loss per job. Priced by crew size, not per seat — $79/mo for a 10-man crew.

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