St. Mary's County, MD Property Tax: $3,392/yr (2026)
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The effective property tax rate in St. Mary's County is 0.87% of assessed home value. On a home at the county median value of $390,900, that works out to about $3,401 per year, or $283 per month. St. Mary's County is located in southern Maryland, with Leonardtown as its county seat, and is home to approximately 114,372 residents.
About St. Mary's County
St. Mary's County covers approximately 358.6 square miles in Maryland. The county is home to about 114,372 residents living in roughly 46,078 housing units, of which 65.8% are owner-occupied. The median household income is $114,580, and the median home was built in 1992.
The county seat is Leonardtown. St. Mary's County borders Calvert County, Charles County, Dorchester County, Somerset County, Northumberland County — useful comparisons if you're considering nearby areas with potentially different tax rates.
How Property Taxes Work in Maryland
Property taxes in Maryland are administered at the county level. Each county sets a millage rate applied to the assessed value of real property — the effective rate above accounts for any partial assessments and exemptions already built into the local tax base. Assessed value can differ meaningfully from current market value depending on how often the county reassesses and what fraction of market value it uses.
Most counties in Maryland offer exemptions that reduce the taxable assessed value: homestead exemptions for primary residences, senior exemptions, disability exemptions, and veteran exemptions are common. These reduce your effective rate below the county-wide average shown here. Contact the St. Mary's County Assessor's office to learn which exemptions apply to your property and when to file.
St. Mary's County vs. Neighboring Counties
| Location | Eff. Rate | Median Home | Annual Tax |
|---|---|---|---|
| St. Mary's County, MD | 0.87% | $390,900 | $3,401 |
| Maryland state average | 0.96% | — | $3,753* |
| Calvert County | 0.88% | $440,200 | $3,858 |
| Charles County | 1.04% | $402,300 | $4,179 |
| Dorchester County | 0.95% | $252,300 | $2,399 |
| Somerset County | 0.98% | $164,300 | $1,603 |
| Northumberland County | 0.48% | $333,100 | $1,602 |
| US national average | 1.10% | $281,900 | $3,101 |
*State average annual tax computed at St. Mary's County's median home value of $390,900. Source: US Census ACS 2023 5-year estimates.
Frequently Asked Questions
How does St. Mary's County's property tax rate compare to the rest of Maryland?
At 0.87%, St. Mary's County is lower than the Maryland state average of 0.96%. On a home at the county median of $390,900, that means about $3,401 per year — versus $3,753 at the state average rate, a difference of $352 per year. Compared to the national average of 1.10%, St. Mary's County is below average.
What's a typical annual property tax bill in St. Mary's County?
For a home at the county median value of $390,900, the annual property tax in St. Mary's County is approximately $3,401 — or about $283 per month. For a home worth $586,350, expect around $5,101 per year. For a $781,800 home, approximately $6,802 per year. Use the calculator above to estimate taxes for any assessed value.
Where do I appeal a St. Mary's County property tax assessment?
Property assessment appeals in St. Mary's County are handled by the St. Mary's County Assessor's office in Leonardtown. Most jurisdictions require filing within 30–90 days of receiving your assessment notice — confirm the specific deadline with the assessor's office before submitting, as deadlines and procedures vary by county. A successful appeal can reduce your assessed value and lower your tax bill for the current and future tax years.
What exemptions are available in St. Mary's County?
Maryland counties commonly offer homestead exemptions for owner-occupied primary residences, senior citizen exemptions for qualifying homeowners aged 65 and older, exemptions for disabled residents, and veterans' exemptions. Each exemption reduces your assessed taxable value, which in turn reduces your effective tax rate below the county-wide 0.87% shown here. Contact the St. Mary's County Assessor's office to confirm which exemptions are available and the application deadlines.
Data sources: US Census Bureau ACS 2023 5-Year Estimates, US Census Gazetteer (2024), County Adjacency File