Workers comp premium estimator

Workers comp premium calculator — how the rate actually works

Workers compensation insurance is calculated differently from most other policies. Instead of a flat annual premium, it scales with your payroll — the more you pay employees, the more premium you owe. The formula is: premium = (payroll ÷ 100) × base rate × experience modifier. Each of those three numbers has real leverage.

How workers comp is calculated — per $100 of payroll

Every class code has a base rate expressed as dollars per $100 of payroll. An electrician (class 5190) at a 4.5% base rate means you pay $4.50 in premium for every $100 of electrician payroll. A $200,000 annual payroll × $4.50 / $100 = $9,000 before the experience modifier.

For a roofer (class 5551) at 27%: that same $200,000 payroll costs $54,000 in premium. The risk differential between office work and roofing is reflected directly in the rate.

Experience modifier (e-mod) — your claims track record

The experience modifier (also called EMR — experience modification rate) adjusts your premium based on your company's actual claims history vs. the industry average for your size and class.

• E-mod 1.0: you are average. No adjustment.
• E-mod 0.8: you are 20% better than average — 20% premium discount. A safety-conscious roofing company with strong return-to-work programs can achieve this.
• E-mod 1.5: 50% above average claims — 50% surcharge. A $9,000 base premium becomes $13,500.
• E-mod 2.0: double the average. Some carriers won't write coverage; you may be forced into the state fund.

Your e-mod is calculated by your state's rating bureau (NCCI in most states) using 3 years of claim data, excluding the most recent policy year. You receive a new e-mod each year.

Why roofing class code has the highest rate

Falls account for over one-third of all construction fatalities. Roofing has the highest fall exposure of any trade — workers are on pitched or flat surfaces with limited fall protection, carrying heavy materials, often in weather conditions. A single serious fall claim can cost $200,000–$500,000 in medical and wage replacement.

Roofing contractors with e-mods below 0.8 command significant pricing advantages on bids. Every dollar invested in fall protection training, personal protective equipment, and formal safety programs can return 5–10× in reduced premium over time.

How to keep your e-mod low

• Return-to-work programs: offering modified duty to injured workers reduces the indemnity (wage loss) portion of claims, which is weighted most heavily in e-mod calculations.
• Safety training: documented OSHA 10/30 training, toolbox talks, and safety meetings. Carriers may offer premium credits for formal programs.
• Drug testing: pre-employment and post-accident testing. Many states give premium credits for drug-free workplace certification.
• Incident reporting discipline: report claims promptly. Delayed reporting increases costs and can increase your e-mod.
• Dispute questionable claims: legitimate claims must be paid, but fraudulent or inflated claims should be investigated and contested with your carrier.

State fund vs private carrier

Most states allow both private carriers and a state fund. A few states (North Dakota, Ohio, Washington, Wyoming) are monopolistic — all workers comp must be purchased from the state fund. Private carriers can offer pricing flexibility, loss control services, and risk management tools that state funds typically cannot. If your e-mod is high, some private carriers will decline coverage, forcing you to the assigned risk pool (state fund) at the highest rates.

Payroll audit — true-up at year end

Your policy premium is based on estimated annual payroll. At the end of each policy year, your carrier audits actual payroll using your tax records, certified payroll, and time records. If you hired more people than estimated — common in a growth year — you'll owe additional premium at audit. This is a frequent cash flow surprise for growing contractors.

Misclassification risk: classifying employees in lower-rated codes than their actual work is the most common workers comp audit finding. A laborer doing roofing work who is coded as a driver (lower rate) will be reclassified at audit — with back premium, interest, and potential policy cancellation. The risk is not worth it.