Illinois Prevailing Wage Calculator
Calculate total prevailing wage costs for Illinois public works projects per the Illinois Prevailing Wage Act (820 ILCS 130). Enter the trade classification, hours worked, and applicable rates to determine gross wages, fringe benefits, and total project labor costs.
Formula
Straight-Time Wages = Straight-Time Hours × Base Rate
Overtime Wages = Overtime Hours × (Base Rate × 1.5)
Fringe Benefits = (Straight-Time Hours + Overtime Hours) × Fringe Rate
Note: Illinois law requires fringe benefits to be paid at the straight-time rate for all hours, including overtime hours.
Total Prevailing Wage Cost = Straight-Time Wages + Overtime Wages + Fringe Benefits
Effective All-In Hourly Rate = Total Prevailing Wage Cost ÷ Total Hours Worked
Total Hours = (Straight-Time Hrs + Overtime Hrs) × Workers × Weeks
Assumptions & References
- Governed by the Illinois Prevailing Wage Act (820 ILCS 130/), which applies to all public works contracts in Illinois.
- Overtime is defined as hours worked beyond 8 hours per day or 40 hours per week, paid at a minimum of 1.5× the base hourly rate.
- Fringe benefits (health & welfare, pension, vacation, apprenticeship) are paid at the straight-time rate for all hours, including overtime, per standard Illinois collective bargaining agreements.
- Prevailing wage rates are set by the Illinois Department of Labor (IDOL) and updated annually each June. Rates shown are illustrative Cook County averages — always verify current rates at labor.illinois.gov.
- Rates vary by county; this calculator uses Cook County rates as defaults. Contractors must use the rates for the county where work is performed.
- Public bodies must post prevailing wage rates on the job site and include them in all contracts per 820 ILCS 130/4.
- This calculator does not include employer payroll taxes (FICA, FUTA, SUTA), workers' compensation insurance, or general liability insurance, which add approximately 25–35% to base wages.
- Apprentices may be paid a percentage of the journeyman rate per approved apprenticeship program ratios.
Illinois public works contractors face civil penalties of up to $500 per day per violation under the Illinois Prevailing Wage Act (820 ILCS 130), making accurate wage calculation a compliance requirement rather than an optional financial exercise. Errors in worker classification, fringe benefit accounting, or county-rate application produce underpayment liabilities that compound quickly across a multi-trade crew working a 20-week project.
What the Illinois Prevailing Wage Calculator Does
The calculator estimates the total prevailing wage cost for a public works project by combining four inputs: the applicable county, the worker classification (trade), the number of workers in each trade, and the total hours per worker. It outputs a gross wage floor per worker, a fringe benefit obligation, and a combined project labor floor. These outputs align with the monthly rate schedules published by the Illinois Department of Labor, which sets rates by county and craft classification.
Core Formula
Total Prevailing Wage Cost = (Basic Hourly Rate × Total Hours) + (Fringe Benefit Rate × Total Hours)
Where: - Basic Hourly Rate = the straight-time or overtime wage floor for the trade in the applicable county - Fringe Benefit Rate = the per-hour employer contribution to health, pension, vacation, and apprenticeship funds - Total Hours = sum of all hours worked by each employee in that trade classification
Overtime multipliers apply when workers exceed 8 hours in a single day or 40 hours in a single workweek, consistent with the Act's overtime provisions under 820 ILCS 130.
Required Inputs
1. County
Illinois has 102 counties. Prevailing wage rates differ by county and are updated annually, typically each June. A carpenter in Cook County earns a higher prevailing wage than the same classification in Adams County. Always pull the current county-specific schedule from the Illinois Department of Labor prevailing wage page before entering a rate.
2. Trade Classification
The IDOL recognizes dozens of trade classifications, including but not limited to: Carpenter, Laborer, Operating Engineer, Electrician, Ironworker, Pipefitter, and Truck Driver. Each classification carries its own straight-time rate, overtime rate, and fringe benefit rate. Misclassifying a worker — for instance, listing a structural ironworker as a laborer — is the most common source of underpayment findings during Illinois Department of Labor audits.
3. Straight-Time vs. Overtime Hours
Enter hours in two separate buckets: - Straight-time hours: All hours at the base rate (generally up to 8 per day) - Overtime hours: Hours beyond the daily or weekly threshold, calculated at 1.5× the basic rate
Some trades under collective bargaining agreements recognized by IDOL schedule double-time on Sundays and holidays; verify the applicable schedule for the specific trade.
4. Fringe Benefit Rate
Fringe benefits under the Act include health and welfare contributions, pension payments, vacation accrual, and apprenticeship fund contributions (according to IDOL). These are expressed as a dollar-per-hour figure alongside the basic wage rate in each county's published schedule. Fringe benefits are legally mandatory and cannot be substituted by an equivalent cash wage payment without violating the Act.
Federal Layer: Davis-Bacon Interaction
Federally funded projects in Illinois trigger both state prevailing wage law and the Davis-Bacon and Related Acts administered by the U.S. Department of Labor. When both apply, the contractor must pay whichever rate is higher on a classification-by-classification basis. The U.S. Department of Labor Wage and Hour Division publishes federal wage determinations applicable to Illinois through the SAM.gov Wage Determinations database. A highway project receiving federal highway funds, for example, would compare Illinois IDOL rates against the applicable federal wage determination and apply the higher figure for each trade.
Certified Payroll and Recordkeeping
Every contractor and subcontractor on a covered Illinois public works project must submit certified payroll records to the public body that awarded the contract. Under 820 ILCS 130, these records must show: - Worker name and address - Trade classification - Hours worked each day - Hourly wage paid - Gross wages earned - Fringe benefits paid or provided
The federal analog — certified payroll requirements under the Electronic Code of Federal Regulations, Title 29 — uses a WH-347 form and carries parallel requirements for federally funded work. Illinois does not mandate use of WH-347 for state-only projects, but the data fields are substantially identical.
Common Calculation Errors
Blended rate averaging: Averaging wages across classifications to simplify payroll is not permitted. Each worker's hours must be compensated at the rate for the actual trade performed during those specific hours.
Omitting fringe benefits from the cost model: Project budgets that treat the basic hourly rate as the full labor cost systematically underestimate labor floors by 20% to 40% in high-benefit trades such as Operating Engineers and Pipefitters (according to IDOL published schedules).
Using prior-year rates: IDOL rate updates typically take effect in late June or early July each year. A project bid in May using the current schedule may carry into a new rate year; the contract documents should specify which rates govern mid-project rate changes.
Misidentifying covered work: The Act applies to construction of public works — work paid for in whole or in part by public funds. Private development receiving tax increment financing may trigger coverage depending on the structure of the public funding (according to IDOL compliance guidance).
FAQ
What is the penalty for underpaying prevailing wages in Illinois?
Under 820 ILCS 130, contractors found in violation owe back wages to affected workers plus a penalty of 2% of unpaid wages per month, and the Illinois Department of Labor can debar non-compliant contractors from public works projects for up to 4 years.
Where are Illinois prevailing wage rates published?
The Illinois Department of Labor publishes county-by-county rate schedules, updated annually. Public bodies awarding contracts must post the applicable schedules at the job site.
Does the Illinois Prevailing Wage Act cover residential construction?
The Act covers public works projects — those funded by a public body. Purely private residential construction is not covered regardless of scale (according to 820 ILCS 130 scope provisions).
How does overtime work under Illinois prevailing wage rules?
Overtime thresholds and multipliers are set per trade classification in each county's schedule, not by a single statewide rule. Some trades trigger overtime after 8 hours in a day; others after 40 hours in a week. The applicable collective bargaining agreement framework governs the schedule published by IDOL.
Are apprentices paid the same prevailing wage rate as journeyworkers?
Apprentices enrolled in programs approved by the Illinois Department of Labor may be paid a percentage of the journeyworker rate, typically ranging from 50% to 90% depending on apprenticeship level (according to IDOL apprenticeship provisions).