What Is a Common Level Ratio Exactly?

If you’re a property owner in Pennsylvania exploring a property tax appeal, you’ve likely come across the term common level ratio (CLR). It sounds technical—and it is—but understanding it is key to knowing whether your property is overassessed and if you may be paying more in taxes than you should.

So, what is a common level ratio?

At its core, the common level ratio is a tool used to equalize property assessments across Pennsylvania counties. Because real estate markets change quickly, and assessments don’t always keep up, the CLR is used to account for these discrepancies and ensure fairness in tax appeals.

Each year, the Pennsylvania State Tax Equalization Board (STEB) calculates the common level ratio for every county. They do this by comparing the assessed values of recently sold properties to their actual sale prices. The result is a ratio that reflects how current assessments stack up to market value.

Let’s walk through an example.

Say your property in Lancaster County is assessed at $500,000. If the county’s common level ratio is 0.80, that means assessments, on average, reflect 80% of market value. To determine what the county believes your home is worth, divide the assessed value by the CLR:

In this example, the county is essentially saying your property’s implied market value is $625,000. If your property would not sell for that amount in today’s market, you may have grounds for an appeal.

Why Does it Matter?

Pennsylvania doesn’t reassess properties annually. Some counties go decades without a full reassessment. That means two nearly identical properties in the same neighborhood can have wildly different tax bills—simply because one was assessed years ago at a different market cycle.

The common level ratio helps adjust for these disparities. It’s particularly important in tax appeals because Pennsylvania law allows property owners to challenge their assessments based on actual market value, adjusted by the county’s CLR.

In practical terms, if your property’s market value is lower than its implied value using the CLR, you may have a strong case.

County Variations

One important note: common level ratios vary significantly from one county to the next. In 2024, for example, Allegheny County had a CLR of just 0.54, while Chester County was closer to 0.84. That’s a major swing—and it directly affects appeal strategy.

If you’re considering a property tax appeal, you’ll definitely want to both understand and check your county’s current CLR and how it compares to recent sales in your area. There even have been instances as precedent set in the judicial system, where you could attempt to try and file an appeal based on a differing of opinion on your property’s common level ratio.