Example data
Sample scenario for estimating a small commercial fit-out.
| Item | Value | Notes |
|---|---|---|
| Duration | 6 months | One-time items spread across months |
| Base recurring/month | 46,100.00 | Labor + materials + equipment + others |
| Overhead | 8% | Applied to direct costs |
| Contingency | 7% | Applied to direct + overhead |
| Tax | 3% | Applied before financing |
| Escalation | 0% / month | Set to 0 for stable recurring costs |
Formula used
Direct costs
Direct = OneTimeTotal + RecurringTotal
Recurring total with escalation
If monthly escalation is r and base recurring is M:
RecurringTotal = M * months (if r = 0)
RecurringTotal = M * (( (1+r)^months - 1 ) / r) (if r > 0)
Overhead and contingency
Overhead = Direct * overhead%
Contingency = (Direct + Overhead) * contingency%
Tax and financing
Tax = (Direct + Overhead + Contingency) * tax%
Financing is an approximation using average outstanding balance:
Finance ≈ (AfterTax * financed%) * annualRate% * (months/24)
Final totals: GrandTotal = AfterTax + Finance, MonthlyAverage = GrandTotal / months.
How to use this calculator
- Enter your project duration in months.
- Fill one-time items such as permits and mobilization.
- Add recurring monthly costs for labor, materials, and rentals.
- Set overhead, contingency, and tax rates if applicable.
- Use escalation if recurring costs rise month to month.
- Press Calculate to see totals and monthly breakdown.
- Download CSV or PDF to share and archive the estimate.
Tip: Run two scenarios with different rates to compare budget risk.
Monthly cost planning guidance
1) Understand cost drivers
Monthly construction spending is shaped by labor hours, material lead times, equipment utilization, and subcontractor sequencing. Track the base recurring total first, then verify it against the schedule and crew loading. A small change in daily labor count or rental days can materially shift the month-end forecast.
2) Separate one-time and recurring items
Preconstruction fees, mobilization, initial procurement, and insurance setup are commonly paid early. This calculator spreads those one-time items across the duration to show an average monthly view. For cashflow control, also note which line items hit in Month 1 versus later months.
3) Apply escalation with discipline
When recurring costs rise over time, a monthly escalation rate models inflation or productivity drag. The recurring total uses a geometric series so later months carry higher cost weight. Keep escalation conservative and document the basis, such as supplier indexes or contract clauses.
4) Add overhead, contingency, and taxes
Overhead covers supervision, project controls, and general site management not captured in direct lines. Contingency protects against scope gaps, rework, and market volatility. Taxes vary by jurisdiction and contract structure, so apply the correct rate to the correct subtotal.
5) Communicate results and keep auditable records
Share the monthly average, total project cost, and key assumptions with stakeholders. Use the CSV or PDF export to preserve inputs, rates, and computed totals for review cycles. Re-run scenarios when duration, procurement strategy, or financing terms change to maintain control.
FAQs
What does “average monthly cost” represent?
It is the total project cost divided by the project duration in months. One-time items are spread across months to show a consistent planning value, not the exact cash paid each month.
How should I enter materials costs?
Put repeat monthly purchases in recurring materials. Put bulk procurement and initial stocking in one-time initial materials. If your buying peaks mid-project, run multiple scenarios to reflect that timing.
When should I use escalation?
Use escalation when labor rates, rentals, or supplies are expected to increase month to month. Keep the rate modest and explain its source, such as supplier quotes, wage agreements, or inflation expectations.
Is the financing cost exact?
It is an approximation based on a financed portion and an average outstanding balance assumption. For high accuracy, build a monthly draw schedule and compute interest on the actual planned balances.
How do overhead and contingency differ?
Overhead funds ongoing management and support functions. Contingency is a risk buffer for uncertainty, scope gaps, and volatility. Keep them separate so stakeholders can see operational cost versus risk protection.
What duration should I use for change orders?
Use the remaining months that the change will affect. If the change is short-term, reduce the duration to match. This keeps the monthly average meaningful for the period you are funding.
How do I share the estimate with my team?
Calculate results, then use the download buttons to export a CSV for spreadsheets or a PDF for signoff. Exports include key inputs and totals so reviewers can validate assumptions quickly.
Note: Financing uses a simplified average-balance estimate. For detailed cashflow schedules, pair this with a monthly draw plan.