How is Washington workers' comp premium calculated?

Unlike most states, Washington L&I charges by hours worked, not payroll. Premium equals total worker hours multiplied by the class code's composite per-hour rate, then adjusted by your experience modification factor.

Can Washington employers deduct part of the cost from workers?

Yes. Washington uniquely lets employers withhold roughly half of the medical-aid and supplemental-pension portion from employee wages. The accident-fund portion is employer-paid only.

What is an experience modification factor?

It is a multiplier above or below 1.0 that reflects your claims history versus similar employers. A mod of 1.20 raises premium 20%; a mod of 0.85 lowers it 15%. New employers start at 1.0.

Do I use private insurance or state fund in Washington?

Washington is a monopolistic state fund: nearly all employers buy coverage directly from L&I, not private carriers. Only self-insured employers approved by L&I are exempt, so this tool models the state fund.

Are part-time hours counted the same way?

Yes. Because premium is hours-based, part-time and overtime hours are summed into total reportable hours and multiplied by the same composite rate, with caps on hours per worker per period.

Washington Workers' Compensation Premium Calculator

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Washington is unusual: its Department of Labor & Industries (L&I) charges workers’ compensation premium by hours worked, not by payroll dollars. This calculator multiplies your reportable hours by the class code’s composite per-hour rate, applies your experience modification factor, and shows the employer and worker-paid split.

How it works

Each L&I risk classification publishes a composite hourly rate that bundles the accident fund, medical-aid fund, and supplemental-pension fund. The base premium is:

premium = total worker hours × composite rate per hour × experience mod

Washington also lets employers deduct roughly half of the medical-aid and stay-at-work portions from employee wages. The accident-fund portion is always employer-paid. This tool models a simplified 50/50 split of the worker-eligible portion so you can see both sides.

Example

A roofing crew logging 8,000 hours in a quarter at a composite rate of $2.50 per hour with an experience mod of 1.10 owes 8,000 × $2.50 × 1.10 = $22,000 in premium for that period. If half is worker-eligible, about $11,000 may be withheld from wages and $11,000 paid by the employer.

Notes

Composite rates vary widely by class code — from cents per hour for clerical work to several dollars for high-risk trades. Enter the exact rate from your L&I account. This is an estimate, not insurance advice; the precise employer versus worker split depends on the specific fund components in your class code. Confirm figures with the Washington L&I rate notice.