Assessed value per square foot: the number that makes comparisons possible
Raw assessments cannot be compared. Rates can.
One number makes property assessments comparable to each other: improvement assessed value divided by building floor area. Everything in a uniformity appeal runs on it.
Why per square foot
Raw assessments cannot be compared. A $40,000 assessment on a 3,000 square foot house and a $30,000 assessment on a 1,500 square foot house tell you nothing on their own — but $13.33 against $20.00 per square foot tells you a great deal.
Dividing by area normalises for the one difference that matters most, which is why assessors themselves work in these terms.
Use the improvement figure, not the total
This is the error that invalidates most amateur comparisons, so it is worth stating precisely.
Your assessment is land plus improvement. The building's floor area is the area of the building only. So dividing the total by the building area mixes land value into a per-square- foot-of-building figure.
A worked example
| Property | Improvement | Floor area | $ / sq ft |
|---|---|---|---|
| Yours | $28,400 | 1,780 | $15.96 |
| Comparable 1 | $23,100 | 1,720 | $13.43 |
| Comparable 2 | $24,800 | 1,840 | $13.48 |
| Comparable 3 | $22,600 | 1,690 | $13.37 |
| Comparable 4 | $25,900 | 1,900 | $13.63 |
The median of the comparables is about $13.48. Applied to your 1,780 square feet, that supports an improvement assessment of $23,994 — a reduction of roughly $4,400, which you then add your unchanged land value back to in order to state the total you are requesting.
Reading the spread, not just the gap
The example above is persuasive because the comparables agree with each other. Their range is 26 cents — about 2% — while the subject is 18% above them. The signal is far larger than the noise.
Now imagine the same subject against comparables at $11.20, $13.50, $15.80 and $17.10. The median is similar, but they disagree among themselves by more than the subject's gap. That is not a finding; it is a scattered sample, and an office will treat it as one.
The test: is the gap between you and the median larger than the spread among the comparables themselves? If not, tighten the group before filing.
Where the arithmetic goes wrong
- Your own floor area is wrong. Check it first — everything else depends on it.
- Mixed tax years. Every figure must come from the same year.
- Post-exemption values. Compare assessments, not taxable values.
- Comparables far from your size. Assessment per square foot is not linear, so a much larger comparable will show a lower rate for reasons that have nothing to do with fairness.