Why does whose fault it is change the number so much?

Because two separate mechanisms turn on it. Liquidated damages are the employer's remedy for late completion and stop the moment an extension of time is granted, whatever caused the delay. Prolongation — the cost of keeping the site open longer — is a real cost somebody bears, and who bears it depends on whether the delaying event carries money as well as time. A neutral event such as exceptional weather earns time but not money, so the contractor keeps the prolongation; an employer delay earns both. That is why the same six weeks can cost 47,100, 26,100, or nothing at all.

What does the damages cap do to an acceleration decision?

It reverses the intuition. Before the cap, every week of delay costs damages plus prolongation, so buying time back is valuable. After it, a further week costs only the prolongation, and the value of catching up drops by the damages rate overnight. On the worked figures the marginal week falls from 7,850 to 4,350 — nearly half — so an acceleration priced against the pre-cap figure overpays substantially. The saving shown here already handles it, because it prices the LAST weeks of the delay rather than the average, and those are the weeks acceleration removes first.

Should I accelerate whenever the saving exceeds the cost?

It is the right starting point and it is not the whole decision. Halve the weeks you expect to recover and run it again first: acceleration plans routinely deliver about half what they promise, because the binding constraint is usually a sequence, an inspection or a lead time rather than labour hours, and doubling the crew on a face that only holds one crew buys nothing. Then look at what the arithmetic cannot see — a late handover can cost a relationship, a follow-on contract, or a place on the next tender list, and none of that appears in a weekly rate.

Where does the weekly prolongation figure come from?

The time-related half of your preliminaries: site staff, accommodation, welfare, temporary services and plant standing on hire. Not the fixed charges — setting up and clearing away are paid once and a delay does not repeat them, so including them overstates the claim and gets it reduced as soon as anyone examines it. The Preliminaries calculator on this site produces exactly this figure and separates it for that reason.

Can the employer deduct damages before the job finishes?

Under most standard forms, only once the completion date has passed and only after the certificate or notice the contract requires — often a non-completion certificate followed by a written notice of intention to deduct. A deduction made without those steps is usually recoverable by the contractor, which is why the interim valuation on this site asks for deductions properly notified rather than deductions intended. The sequence matters as much as the entitlement.

Financial-Adjacent

Delay Cost and Acceleration Break-Even Calculator

What a week of delay costs once damages, prolongation and the damages cap are all in — and the most it is worth spending to recover it.

Answers as you typeNo submit button
Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Weeks of Delay

How far past the completion date the job is expected to finish.

Use the forecast overrun, not the delay accrued so far — the decision to accelerate is made against where the programme is heading. If some of the overrun is already covered by an extension of time that has been granted, deduct those weeks and run only what remains, because they are a different case with a different answer.

Whose Delay Is It

Which of the three cases applies, because they cost completely different amounts.

A culpable week carries damages AND prolongation, both on the contractor. A neutral event — exceptional weather is the usual example — earns an extension that stops the damages, but nobody pays for the extra weeks, so the prolongation is still yours. An employer delay earns both an extension and loss and expense, so in principle it costs nothing. In principle: an entitlement that was never notified in the form and within the period the contract requires is routinely lost, and this page assumes notice was given properly.

Liquidated Damages Per Week

The rate stated in the contract, not an estimate of the employer's loss.

Liquidated damages are pre-agreed precisely so nobody has to prove actual loss, so the figure comes off the contract particulars and nowhere else. A rate set so high that it is a penalty rather than a genuine pre-estimate of loss may be unenforceable in some jurisdictions — but that is an argument to have with a lawyer, not a reason to plan around a lower number.

Maximum Damages

The total damages cap in the contract. Enter 0 if there is no cap.

Commonly stated as a percentage of the contract sum — 5% and 10% are both ordinary — which on a 900,000 contract at 10% is 90,000. The cap matters more than it looks: once it is reached, further delay costs only the prolongation, so the value of catching up falls sharply at exactly the moment the job feels most urgent. Enter 0 only if the contract genuinely has no limit, which is unusual and worth checking rather than assuming.

Time-Related Preliminaries Per Week

What the site costs to keep open for a week: staff, accommodation, services, plant standing.

The Preliminaries calculator on this site produces exactly this figure and labels it as the cost of one week's delay. It must exclude the fixed charges — setting up and clearing away — because a delay does not repeat those, and a prolongation claim that includes them will be reduced by the amount as soon as anyone looks.

Cost of Acceleration Being Considered

What overtime, extra crews or additional plant would cost to recover the time.

Price it honestly, including what acceleration does to productivity rather than only what it adds to the wage bill. Sustained overtime loses output per hour, a second crew on the same face gets in the way of the first, and both raise the defect rate — so the real cost of buying back four weeks is usually well above four weeks of extra labour. Enter zero if you only want the cost of the delay itself.

Weeks That Acceleration Would Recover

How much of the delay the spend above would actually claw back.

Be pessimistic. Acceleration plans routinely deliver about half what they promise, because the constraint is usually not labour hours — it is a sequence, an inspection, a lead time or a single trade that cannot be doubled up. Recovering fewer weeks than planned while paying the full cost is the normal outcome, and it is worth running this at half the optimistic figure to see whether the decision survives.

Cost of the delay

$47,100

High confidence

Recovering 4 weeks saves 31400 against a spend of 30000, so accelerating is worth 1400 on these figures. Before committing, halve the weeks recovered and run it again — acceleration plans routinely deliver about half what they promise, because the constraint is usually a sequence or a lead time rather than labour hours, and a plan that only survives at the optimistic figure is not a plan.

Liquidated damages: $21,000
Prolongation borne: $26,100
Saving from recovering 4 week(s): $31,400
Cost of that acceleration: $30,000
Net of accelerating: $1,400
Most it is worth spending to recover those weeks: $31,400

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

Liquidated damages are a pre-agreed rate stated in the contract, recoverable without proof of actual loss, and in most standard forms subject to a stated maximum expressed as a percentage of the contract sum; once that maximum is reached no further damages accrue however long the delay continues
Standard forms distinguish culpable delay (damages apply, prolongation borne by the contractor), excusable non-compensable delay such as exceptional weather (an extension of time stops damages but carries no money), and excusable compensable delay caused by the employer (an extension plus loss and expense, which recovers time-related costs)
Loss and expense for prolongation is evaluated on the time-related preliminaries actually incurred over the extended period, not as a percentage of the contract sum, and requires notice and substantiation under every standard form

Inputs used

Weeks of Delay: 6
Whose Delay Is It: The contractor's — damages run, prolongation borne
Liquidated Damages Per Week: 3500
Maximum Damages: 90000
Time-Related Preliminaries Per Week: 4350
Cost of Acceleration Being Considered: 30000
Weeks That Acceleration Would Recover: 4

Intermediate steps

Liquidated damages: $21,000
Prolongation borne: $26,100
Saving from recovering 4 week(s): $31,400
Cost of that acceleration: $30,000
Net of accelerating: $1,400
Most it is worth spending to recover those weeks: $31,400

Final result$47,100

Confidence note: Recovering 4 weeks saves 31400 against a spend of 30000, so accelerating is worth 1400 on these figures. Before committing, halve the weeks recovered and run it again — acceleration plans routinely deliver about half what they promise, because the constraint is usually a sequence or a lead time rather than labour hours, and a plan that only survives at the optimistic figure is not a plan.

What this calculation does not cover

The contract governs. The damages rate, the cap, what counts as an excusable event and the notice a claim requires are all in it and none of them are here.
Assumes any entitlement has been properly notified within the contractual period. Unnotified entitlement is routinely worth nothing whatever its merits.
Damages are treated as running weekly. Some contracts state them per day or per calendar month, and a partial period then rounds differently.
Acceleration is priced as a single figure you supply, not modelled. Lost productivity under sustained overtime and trade stacking are real and belong inside that figure.
Consequential losses beyond the contract's damages — a lost tenancy, a missed season, a reputational cost — are outside a liquidated damages regime and outside this page.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.0

Regulatory standards & verification citations3

Liquidated damages are a pre-agreed rate stated in the contract, recoverable without proof of actual loss, and in most standard forms subject to a stated maximum expressed as a percentage of the contract sum; once that maximum is reached no further damages accrue however long the delay continues
Standard forms distinguish culpable delay (damages apply, prolongation borne by the contractor), excusable non-compensable delay such as exceptional weather (an extension of time stops damages but carries no money), and excusable compensable delay caused by the employer (an extension plus loss and expense, which recovers time-related costs)
Loss and expense for prolongation is evaluated on the time-related preliminaries actually incurred over the extended period, not as a percentage of the contract sum, and requires notice and substantiation under every standard form

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for.

Delay, Notice and Extension of Time

How to calculate delay cost and acceleration break-even in 8 steps

Weeks of DelayHow far past the completion date the job is expected to finish.
Whose Delay Is ItWhich of the three cases applies, because they cost completely different amounts.
Liquidated Damages Per WeekThe rate stated in the contract, not an estimate of the employer's loss.
Maximum DamagesThe total damages cap in the contract. Enter 0 if there is no cap.
Time-Related Preliminaries Per WeekWhat the site costs to keep open for a week: staff, accommodation, services, plant standing.
Cost of Acceleration Being ConsideredWhat overtime, extra crews or additional plant would cost to recover the time.
Weeks That Acceleration Would RecoverHow much of the delay the spend above would actually claw back.
Cost of the delayThe tool computes the cost of the delay from those figures and shows the formula, its sources, and a confidence rating alongside it.

Cost of the delay by weeks of delay

Page defaults, not your figures above.

Weeks of Delay	Cost of the delay (currency)
1	7,850
2	15,700
5	39,250
10	78,500
20	157,000
50	307,500

Frequently asked questions

Why does whose fault it is change the number so much?: Because two separate mechanisms turn on it. Liquidated damages are the employer's remedy for late completion and stop the moment an extension of time is granted, whatever caused the delay. Prolongation — the cost of keeping the site open longer — is a real cost somebody bears, and who bears it depends on whether the delaying event carries money as well as time. A neutral event such as exceptional weather earns time but not money, so the contractor keeps the prolongation; an employer delay earns both. That is why the same six weeks can cost 47,100, 26,100, or nothing at all.
What does the damages cap do to an acceleration decision?: It reverses the intuition. Before the cap, every week of delay costs damages plus prolongation, so buying time back is valuable. After it, a further week costs only the prolongation, and the value of catching up drops by the damages rate overnight. On the worked figures the marginal week falls from 7,850 to 4,350 — nearly half — so an acceleration priced against the pre-cap figure overpays substantially. The saving shown here already handles it, because it prices the LAST weeks of the delay rather than the average, and those are the weeks acceleration removes first.
Should I accelerate whenever the saving exceeds the cost?: It is the right starting point and it is not the whole decision. Halve the weeks you expect to recover and run it again first: acceleration plans routinely deliver about half what they promise, because the binding constraint is usually a sequence, an inspection or a lead time rather than labour hours, and doubling the crew on a face that only holds one crew buys nothing. Then look at what the arithmetic cannot see — a late handover can cost a relationship, a follow-on contract, or a place on the next tender list, and none of that appears in a weekly rate.
Where does the weekly prolongation figure come from?: The time-related half of your preliminaries: site staff, accommodation, welfare, temporary services and plant standing on hire. Not the fixed charges — setting up and clearing away are paid once and a delay does not repeat them, so including them overstates the claim and gets it reduced as soon as anyone examines it. The Preliminaries calculator on this site produces exactly this figure and separates it for that reason.
Can the employer deduct damages before the job finishes?: Under most standard forms, only once the completion date has passed and only after the certificate or notice the contract requires — often a non-completion certificate followed by a written notice of intention to deduct. A deduction made without those steps is usually recoverable by the contractor, which is why the interim valuation on this site asks for deductions properly notified rather than deductions intended. The sequence matters as much as the entitlement.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.