Workers Comp Experience Mod Calculator
The workers compensation experience modification factor (e-mod) adjusts an employer's premium based on their actual claims history relative to the expected losses for businesses in the same industry. This calculator uses a simplified version of the NCCI experience rating formula: the ratio of actual losses (with primary losses given full weight and excess losses given reduced weight via a ballast factor) to expected losses (computed similarly). An e-mod below 1.0 earns a premium discount; above 1.0 triggers a surcharge. Enter the actual and expected loss data for the three-year experience period.
Experience mod formula (simplified NCCI)
E-mod = (Actual primary + W x Actual excess) / (Expected primary + W x Expected excess)
W = ballast/stability weight (0 to 1; smaller employers use lower W)
Primary losses carry full weight (frequency measure); excess losses carry reduced weight W (stability adjustment). The NCCI publishes the primary split point and W factors for each state and employer size annually.
Reducing your experience mod
- Prevent claims through safety programs, proper training, and hazard elimination. Frequency drives primary losses, which have the most impact.
- Actively manage open claims to reach prompt, fair resolution. Reserves for open claims count as incurred losses in the experience period.
- Return-to-work programs reduce lost-time claim costs significantly, lowering both primary and excess losses.
- Verify that your NCCI experience rating worksheet correctly classifies payroll to the right class codes. Misclassifications can inflate expected losses.
- Even a mod reduction from 1.20 to 1.00 on a $100,000 base premium saves $20,000 per year.
Experience mod: frequently asked questions
What is the workers comp experience modification factor?
The experience modification factor (e-mod or EMR) is a multiplier applied to a workers compensation premium that reflects a business's actual loss history compared to the expected losses for businesses in the same industry. An e-mod of 1.00 is average. Below 1.00 is better than average (credit); above 1.00 is worse (debit).
How does NCCI calculate the experience modification?
NCCI's formula separates actual losses into primary losses (first portion of each claim, capturing frequency) and excess losses (amounts above the primary split point, capturing severity). The mod is approximately: Actual primary + Ballast-weighted excess divided by Expected primary + Ballast-weighted excess. Small employers receive more ballast weight for stability.
What years of loss data are used?
The experience period typically covers three policy years, excluding the most recent completed year. For example, a 2026 mod uses 2022, 2023, and 2024 experience. This four-year lookback (with the most recent year excluded) is standard NCCI practice.
How much can the e-mod affect my premium?
The e-mod multiplies directly. An e-mod of 0.75 saves 25 percent of the manual premium; an e-mod of 1.50 adds 50 percent. For large employers, premium swings of tens of thousands of dollars per year are common. Investing in safety programs that reduce frequency directly lowers the e-mod.
What is the difference between primary and excess losses?
Primary losses are the first portion of each claim (typically the first $16,500 to $18,000 depending on state and year). They carry full weight in the mod calculation because they reflect claim frequency, which employers can control. Excess losses (amounts above the primary split) carry reduced weight because severity is harder for employers to control.
Official sources
- NCCI (National Council on Compensation Insurance): Understanding Experience Rating.
- NAIC: NAIC Consumer Resources.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.