The same $500,000 of payroll can cost an Oklahoma employer $1,200 or $60,000 in workers’ comp premium — the difference is entirely in the class code. Premium follows one transparent formula everywhere NCCI rating applies: payroll per $100, times the classification’s base rate, times your experience modifier. This calculator runs that formula so you can budget coverage per class of worker before a broker ever quotes you.
The manual-premium formula
The manual premium is built from three numbers:
- Payroll per 100. Premium is rated per
$100of payroll, so divide annual payroll by 100. - Class code base rate. Each classification code has a rate per
$100reflecting its injury risk — low for clerical, high for construction. - Experience modifier. Multiply by your experience mod, where
1.00is average, below 1.00 is a credit, and above 1.00 is a surcharge.
The formula is: premium = (payroll ÷ 100) × rate × mod
An optional fixed expense constant can be added to match the way real policies are priced.
Worked example
Suppose a small Oklahoma construction subcontractor has $500,000 of carpentry
payroll in a class code rated at $2.50 per $100, with an experience mod of
0.95 (a 5% credit for good loss history):
(500,000 ÷ 100) × 2.50 × 0.95
= 5,000 × 2.50 × 0.95
= $11,875 manual premiumA clerical worker in the same company with $100,000 of payroll at $0.25 per
$100 and the same 0.95 mod costs:
(100,000 ÷ 100) × 0.25 × 0.95 = $237.50The contrast shows why class code selection accuracy matters: misclassifying a construction worker as clerical would dramatically understate the premium, which can lead to a large audit adjustment at policy year-end.
Oklahoma workers’ comp: competitive market, not monopolistic
Some states (like Ohio, Washington, and Wyoming) require employers to buy workers’ comp only from a state-run monopolistic fund. Oklahoma is not one of them. Oklahoma employers can buy coverage from:
- Private insurance carriers — most major commercial insurers write workers’ comp in Oklahoma
- CompSource Mutual — a state-affiliated (but not monopolistic) carrier often used by Oklahoma employers who have difficulty finding coverage in the standard market
- Self-insurance — qualifying large employers can self-insure with state approval and financial guarantees
The competitive market means rates for the same class code can vary between carriers, and employers should shop multiple carriers or work with a commercial insurance broker to compare.
How experience modifiers work
Your experience modifier (mod) is calculated by the National Council on Compensation Insurance (NCCI), which Oklahoma uses. It compares your actual losses over a typically three-year lookback period against the expected losses for your payroll and class codes. Key points:
- A 1.00 mod means your losses exactly match average for your industry
- A mod below 1.00 (for example 0.85) means you’ve had fewer claims than average and earn a premium credit
- A mod above 1.00 (for example 1.25) means you’ve had more claims and pay a surcharge
- Only employers with enough payroll (generally above a threshold, typically around $10,000 in premium) receive a computed mod; smaller employers get 1.00
What this estimate leaves out
The manual premium this tool computes is a starting point. Real Oklahoma workers’ comp policies also add:
- Expense constant — a flat per-policy addition
- Premium discount — larger policies earn a sliding scale discount
- Schedule credits or debits — carrier-applied adjustments for specific workplace safety programs, management quality, or industry factors
- Terrorism and catastrophe surcharges
- Minimum premium — most policies have a floor regardless of payroll
Always obtain formal quotes from licensed carriers for binding premium figures. Oklahoma is a competitive-market state — rates and credits differ by insurer for the same class code.
The payroll-audit trap
Workers’ comp premiums are provisional. You pay based on estimated payroll at policy inception, and the carrier audits actual payroll at year-end — growth means an additional bill, and misclassification means a retroactive re-rate at the correct (higher) class code. Two habits prevent audit pain: keep class-code-accurate payroll records through the year (especially for employees who split time between clerical and field work — many carriers allow a payroll split only if records support it), and re-run this calculator whenever headcount changes materially so the audit adjustment is never a surprise.
Sources
- NCCI — National Council on Compensation Insurance — class codes and experience-rating methodology used in Oklahoma
- CompSource Mutual Insurance Company — Oklahoma’s state-affiliated carrier
Estimate only. Manual premium is the starting point of a quote, not the quote; carrier filings, credits, and assessments move the final figure. All math runs locally in your browser.