Workers compensation premium comes down to three numbers multiplied together: payroll, a class rate, and your experience modifier. Two of the three are largely outside your control in the short term. The third — the modifier — is where the money is, and it is the one most employers treat as weather rather than as something they influence.
Class Code Is the Biggest Single Lever, and It Is Often Wrong
The rate spread across class codes in this calculator runs from $0.35 to $25.00 per $100 of payroll. Nothing else in the formula comes close to that range. A single misassigned code can multiply a premium several times over, and misassignment is common — codes are set by the duties actually performed, not by what the business calls itself or what industry it sits in.
The frequent error is applying one blanket code to a mixed workforce. A construction company's estimators, schedulers, and bookkeepers belong in clerical codes, not the field code, provided their duties are genuinely separate and payroll records substantiate the split. Carriers allow that division when it is documented. They will not volunteer it.
How the Experience Modifier Is Built
Your EMR compares your actual losses to the expected losses for a business of your class and size, computed over a rolling three-year window that excludes the most recent year. Because of that lag, a claim affects your premium for three policy periods after it closes, and a safety improvement takes about that long to show up as savings.
Claim frequency weighs more heavily than claim severity in most rating formulas. Several small reported injuries typically damage a modifier more than one large one, on the theory that frequency predicts future loss better than a single catastrophic event. That inverts the usual intuition — the sprains and stitches matter more than they feel like they should.
Where the Real Savings Are
Start with the loss run. Ask your carrier for it annually and read it. Claims that closed years ago are sometimes still carried with open reserves, which inflates the loss figure feeding your modifier. Getting stale reserves closed is unglamorous administrative work that occasionally moves a modifier by a tenth or more — worth thousands at any real payroll.
Then look at return-to-work. Lost-time claims are weighted far more heavily than medical-only claims, so bringing an injured employee back to genuine light duty rather than leaving them out changes the claim's classification and its rating impact. A documented light-duty program is one of the highest-return safety investments available, and it costs mostly coordination.
Finally, verify payroll classification before the audit rather than after. The end-of-period audit trues up estimated payroll against actual, so understating payroll at binding only defers the bill and can add penalties.
What This Calculator Does Not Model
The figures here are a planning estimate from published class rates, not a quote. Real premiums add and subtract several layers this page does not attempt: schedule rating credits and debits applied at underwriter discretion, premium discounts for larger policies, expense constants and terrorism loadings, assigned-risk surcharges, and state-specific assessments.
Jurisdiction matters more than the single state factor suggests. North Dakota, Ohio, Washington, and Wyoming require coverage through a monopolistic state fund with its own rate schedule entirely. Some states publish advisory rather than mandatory rates, letting carriers file their own — so two carriers can quote materially different premiums on identical payroll and class. Use this to build a budget and to sanity-check a quote, then get the quote.