How is a Massachusetts workers' comp premium calculated?

The core formula is Premium = (Payroll ÷ 100) × Class Rate × Experience Mod. The class rate is a dollar amount per $100 of payroll set for each job classification, and the experience modifier adjusts it for the employer's own claims history. Massachusetts rates are filed through the Workers' Compensation Rating and Inspection Bureau (WCRIBMA).

What is an experience modifier (Mod)?

The experience modification factor compares your past claims to the expected claims for your industry and size. A Mod of 1.0 is average. A Mod of 0.85 means a 15% discount for a better-than-average safety record, while 1.20 means a 20% surcharge. Small or new employers without enough payroll history are assigned a 1.0 Mod.

Why do workers' comp rates vary so much by class code?

Rates reflect injury risk. A clerical office class might be under $0.20 per $100 of payroll, while roofing or structural steel can exceed $10 per $100. Each employee is assigned a governing class code based on their actual duties, and a single business can have several class codes with different rates.

Is Massachusetts a state-fund or private-carrier state?

Massachusetts is a competitive private-market state — coverage is bought from private insurers, not a monopolistic state fund. Employers who cannot find voluntary coverage can obtain it through the assigned-risk pool administered by WCRIBMA. Rates are still based on the same class-code and experience-modifier system.

Does this estimate include taxes, fees, and discounts?

No. This is the manual premium before schedule credits/debits, premium discounts for larger policies, terrorism and catastrophe surcharges, expense constants, and assessments. Your actual quote from a carrier may differ. Use this as a planning estimate and request a formal quote for an accurate figure.

Massachusetts Workers' Compensation Premium Calculator

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This calculator estimates an employer’s annual workers’ compensation premium in Massachusetts using the industry-standard formula. Premium is driven by payroll, the class-code rate for the work being done, and your experience modifier — not by the number of employees. Massachusetts is a competitive private-market state with rates filed through the Workers’ Compensation Rating and Inspection Bureau (WCRIBMA).

How it works

The manual premium formula is:

premium = (annual payroll ÷ 100) × class rate × experience mod

Class rate is a dollar amount per $100 of payroll, set per job classification (low for clerical, high for construction).
Experience mod adjusts for your claims history: 1.0 is average, below 1.0 is a credit, above 1.0 is a debit.

For a business with multiple job types, you would run this once per class code and add the results.

Worked example

A landscaping crew with $400,000 payroll, a class rate of $5.50 per $100, and an experience Mod of 0.90:

Payroll units = $400,000 ÷ 100 = 4,000
Manual premium = 4,000 × $5.50 = $22,000
After Mod = $22,000 × 0.90 = $19,800

Notes

A Mod below 1.0 rewards a strong safety record; above 1.0 penalizes a poor one. New employers use 1.0.
This is the manual premium before schedule credits, premium discounts, surcharges, expense constants, and state assessments — your carrier quote will adjust these.

Disclaimer: Estimate only — not an insurance quote. Class rates and experience modifiers come from WCRIBMA filings and your loss history. Get a formal quote from a licensed Massachusetts carrier or agent for a binding figure.