The two numbers that matter
- Cost to complete (CTC). Your best estimate of the remaining costs to finish the work, from today forward.
- Estimated cost at completion (EAC). Actual cost to date + cost to complete. What the job will ultimately cost if things go as forecast.
Compare EAC to your original budget and you get an honest, forward-looking read: on track, or heading over? The moment EAC drifts above budget, you have a problem you can still do something about, unlike an overrun you discover at close-out.
Three ways to forecast cost to complete
1. Bottom-up re-estimate (most accurate)
Go through the remaining work and re-price it from scratch: labor hours left, materials still to buy, subs not yet paid. Slow, but the most reliable, and worth doing when a job is in trouble.
2. Budget-remaining
Simple: CTC = original budget − actual cost to date. This assumes the rest of the job goes exactly to plan. Fine as a first glance, dangerous as your only method, because it ignores what the job is already telling you about how it's really going.
3. Performance-adjusted (trust the trend)
If you're running 10% over on the work done so far, it's naive to assume the remaining work will magically come in on budget. Adjust the remaining estimate by the performance you've actually seen. This is the essence of earned-value forecasting: let the job's own track record inform the forecast. See the plain-English EVM guide for how this connects to CPI.
A worked example
Bathroom remodel budgeted at $30,000. You're about halfway through the work, but you've already spent $18,000.
- Budget-remaining method: CTC = $30,000 − $18,000 = $12,000. EAC = $30,000. Looks fine.
- Performance-adjusted: you're halfway done but spent 60% of budget, running about 20% hot. If the rest follows suit, the remaining half won't cost $12,000, it'll cost closer to $18,000. EAC is roughly $36,000, so $6,000 over.
Same job, two forecasts. The performance-adjusted view is the one that saves you, because it flags the overrun now, while there's still work left to manage.
Don't forget committed costs
A good CTC forecast leans on what you've already locked in. Signed subs and issued POs are known future costs, so they belong in your remaining estimate at their committed values, not guesses. This is where committed vs. actual cost tracking pays off directly: your commitments are half your forecast already made.
Making it a habit
- Update CTC at least monthly on every open job, and weekly on anything large or shaky.
- Use performance-adjusted forecasting once you have real cost data on the job.
- Fold in committed costs at their known values.
- Act on the gap. If EAC creeps over budget, adjust scope, renegotiate, or price a change order while you still can.
Keep your remaining-work unit costs realistic by cross-checking the Construction Price Index.
Where this fits
Cost-to-complete forecasting is the forward-looking engine of earned value tracking and the difference between reactive and proactive construction project management.
Put it to work
TradesMetrics forecasts cost at completion from the estimate you build in the free estimating tool plus your live costs, so a job going over lights up early, not at close-out. See how it works.