Change Order Drift Calculator

Change orders creep up during construction. This calculator tracks drift.

Contract value

Owner CO

Sub CO

Unforeseen CO

Percent complete

Drift %

4.63%

Total CO

$925,000

Projected final CO %

7.71%

How the math works

Drift = total CO ÷ contract. Projected final = drift × (100 / % complete).

Projected final CO above 10% by 50% complete is a strong flag. At that stage, address scope discipline, freeze owner changes, and reforecast total budget with adjusted contingency. Projects that ignore early drift hit 20-30% final drift almost without exception.

How to Use

Enter contract value.
Enter owner change orders to date.
Enter sub change orders.
Enter unforeseen conditions.
Enter percent complete.
Read drift percentage.

Frequently Asked Questions

Typical drift?

Good project: 3-7% total COs at completion. Moderate: 8-15%. High: 15-30%. Above 30%: severe, indicating bid-design misalignment or scope creep. Drift early (below 20% complete) predicts total drift well.

Categories?

Owner-driven (program changes, upgrades): ~40% of COs on average. Design clarifications (incomplete bid docs): ~30%. Unforeseen conditions: ~15%. Code/inspector driven: ~10%. Weather/schedule: ~5%.

Controlling drift?

Finalize design 90%+ before bid. Test fit through design. Allow no owner changes post-construction-start for 90 days (penalty period). Clear scope. Each cuts CO drift 3-8 points.

Who owns this risk — sponsor or lender?

Construction risks are typically shared: hard-cost overrun owned by sponsor (via completion guaranty), soft-cost and delay risks shared per contract, force-majeure excused but bears owner carry cost. Document risk ownership in the loan agreement and GC contract before closing. Disputes get expensive when roles are unclear. Institutional deals spell out every allocation in writing.