Septic Tank Size Calculator
A 3-bedroom home needs a septic tank of at least 1,000 gallons in 38 of the 47 states that set a size by bedrooms. The lowest state minimum is 900 gallons and the highest 1,500 gallons.
United States · 3 bedrooms
1,000gallons, the smallest tank allowed
The minimum in 38 of the 47 states that set a size for 3 bedrooms. Lowest 900 gallons, highest 1,500 gallons.
Rule: each state's rule
Septic tank sizing chart by number of bedrooms
| Bedrooms | Usual minimum | States | Lowest | Highest |
|---|---|---|---|---|
| 1 bedroom | 1,000 | 32 of 46 | 500 | 1,500 |
| 2 bedrooms | 1,000 | 34 of 47 | 750 | 1,500 |
| 3 bedrooms | 1,000 | 38 of 47 | 900 | 1,500 |
| 4 bedrooms | 1,250 | 18 of 47 | 1,000 | 2,000 |
| 5 bedrooms | 1,500 | 27 of 47 | 1,000 | 2,000 |
| 6 bedrooms | 1,500 | 16 of 42 | 1,260 | 2,500 |
Gallons. States: how many have that minimum, out of those whose rule gives a size for that many bedrooms.
Minimum septic tank size in every state
| State | 1 bed | 2 bed | 3 bed | 4 bed | 5 bed | 6 bed |
|---|---|---|---|---|---|---|
| Alabama | 1,000 | 1,000 | 1,000 | 1,000 | 1,500 | 1,750 |
| Alaska | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Arizona | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 2,000 |
| Arkansas | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Colorado | – | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Connecticut | 1,000 | 1,000 | 1,000 | 1,125 | 1,250 | 1,375 |
| Delaware | 1,000 | 1,000 | 1,000 | 1,000 | 1,500 | 1,500 |
| Florida | 900 | 900 | 900 | 1,050 | 1,200 | 1,350 |
| Georgia | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| Hawaii | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | – |
| Idaho | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| Illinois | 750 | 750 | 1,000 | 1,250 | 1,500 | 1,750 |
| Indiana | 750 | 750 | 1,000 | 1,250 | 1,500 | 1,800 |
| Iowa | 1,250 | 1,250 | 1,250 | 1,500 | 1,750 | 2,000 |
| Kansas | 1,000 | 1,000 | 1,000 | 1,200 | 1,500 | 1,800 |
| Kentucky | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Louisiana | 500 | 750 | 1,000 | 1,250 | 1,500 | 1,750 |
| Maine | 750 | 750 | 1,000 | 1,000 | 1,250 | 1,500 |
| Maryland | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Massachusetts | 1,500 | 1,500 | 1,500 | 1,500 | 1,500 | 1,500 |
| Minnesota | 1,000 | 1,000 | 1,000 | 1,500 | 1,500 | 2,000 |
| Mississippi | 750 | 750 | 900 | 1,000 | 1,250 | 1,500 |
| Missouri | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | – |
| Montana | 1,000 | 1,000 | 1,000 | 1,500 | 1,500 | 2,000 |
| Nebraska | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Nevada | 1,000 | 1,000 | 1,000 | 1,200 | 1,500 | 1,500 |
| New Hampshire | 1,250 | 1,250 | 1,250 | 1,250 | 1,500 | 1,750 |
| New Jersey | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| New Mexico | 750 | 1,000 | 1,000 | 1,200 | 1,500 | 1,500 |
| New York | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| North Carolina | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | – |
| North Dakota | 1,000 | 1,000 | 1,000 | 1,200 | 1,500 | 1,500 |
| Ohio | 1,000 | 1,000 | 1,500 | 2,000 | 2,000 | 2,500 |
| Oklahoma | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| Oregon | 1,000 | 1,000 | 1,000 | 1,000 | 1,500 | 1,500 |
| Pennsylvania | 900 | 900 | 900 | 1,250 | 1,400 | 1,550 |
| Rhode Island | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| South Carolina | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| South Dakota | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Tennessee | 750 | 750 | 900 | 1,000 | 1,250 | 1,500 |
| Texas | 750 | 750 | 1,000 | 1,250 | 1,250 | – |
| Utah | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 | 1,750 |
| Vermont | 1,000 | 1,000 | 1,000 | 1,000 | 1,000 | 1,260 |
| Virginia | 750 | 750 | 900 | 1,200 | 1,500 | – |
| Washington | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| West Virginia | 1,000 | 1,000 | 1,000 | 1,000 | 1,250 | 1,500 |
| Wyoming | 1,000 | 1,000 | 1,000 | 1,000 | 1,150 | 1,300 |
Gallons. A dash: the state's table does not cover that many bedrooms.
What changes the minimum
| State | Rule |
|---|---|
| Arizona | The size also depends on the plumbing fixtures. A home with more than seven fixture units per bedroom moves one size up: three bedrooms 1,250 gallons, four 1,500, five 2,000, six 2,500. |
| Colorado | A grinder pump ahead of the tank adds at least 500 gallons. |
| Connecticut | A garbage grinder adds 250 gallons. A bathtub of 100 to 200 gallons adds 250 gallons, a larger one 500. Where more than 25 percent of the flow is pumped into the tank, the tank is 50 percent larger. |
| Florida | Where the bedrooms and the building area point to different flows, the greater flow applies. |
| Georgia | A garbage disposal adds 50 percent. |
| Illinois | With a garbage grinder: 1,125 gallons for two bedrooms or fewer, 1,500 for three, 2,000 for four, 2,200 for five, 2,600 for six. |
| Kansas | With a garbage disposal the tank must hold three times the daily flow: up to three bedrooms 1,350 gallons, four 1,800, five 2,250. A county with its own sanitary code may ask for more. |
| Kentucky | With a garbage disposal: 250 gallons more at every size. |
| Maine | With a garbage disposal the tank is made at least 30 percent larger, or a second tank, a two-compartment tank or an outlet filter is added. |
| Maryland | The sizes already allow for a garbage disposal. The table is for a home that does not need a nitrogen-reducing (BAT) system. |
| Massachusetts | A garbage disposal calls for a two-compartment tank or two tanks in series. |
| Minnesota | With a garbage disposal, or where sewage is pumped to the tank, the capacity must be at least 50 percent greater. |
| Mississippi | These sizes are for a tank with a baffle or effluent filter. Without one: four bedrooms 1,200 gallons, five 1,500, six 1,800. 130 gallons more for each occupant over two per bedroom. |
| Missouri | The sizes already allow for a garbage disposal. |
| Nebraska | With a garbage disposal or a tub of more than 50 gallons: three bedrooms 1,250 gallons, four 1,500, five 1,750, six 2,000. With both: two bedrooms 1,250 gallons, three 1,500, four 1,750, five 2,000, six 2,250. |
| New Hampshire | With a garbage grinder the capacity is increased by 50%. |
| New Jersey | A garbage disposal or a sewage ejector pump adds 50 percent and calls for a multiple-compartment tank. An expansion attic counts as a bedroom. |
| New York | A garbage grinder counts as one more bedroom. An expansion attic counts as one more bedroom. |
| North Dakota | The sizes already allow for a garbage disposal. |
| Ohio | From three bedrooms up the capacity is in two tanks or compartments. |
| Rhode Island | A garbage disposal adds 250 gallons, and so does a tub of 100 gallons or more. |
| South Dakota | A garbage disposal adds 20 percent. |
| Texas | A home larger than the size given for its bedrooms uses the rate of the next size. With water-saving devices the rates are lower: three bedrooms 750 gallons, four bedrooms 1,000. |
| Utah | An unfinished basement counts as at least one more bedroom. |
| Vermont | A garbage disposal adds at least 50 percent. |
| Wyoming | In the design flow table an unfinished basement counts as two more bedrooms. |
States that size the tank from the daily flow
| State | How the size is worked out |
|---|---|
| Delaware | The design flow of a home is 120 gallons a day per bedroom, at least 240. Up to 500 gallons a day (four bedrooms) the tank holds 1,000 gallons; above that it holds 1.5 times the flow and at least 1,500 gallons (five bedrooms 600 gallons a day, six 720). |
| Florida | Table I gives a daily sewage flow by bedrooms and building area (one bedroom with 750 sq ft or less: 100 gallons; two bedrooms with 751 to 1,200 sq ft: 200; three with 1,201 to 2,250 sq ft: 300; four with 2,251 to 3,300 sq ft: 400; 60 gallons more for each further bedroom or 750 sq ft). Table II turns the flow into a tank: up to 300 gallons a day, 900 gallons; 301 to 400, 1,050; 401 to 500, 1,200; 501 to 600, 1,350. |
| Louisiana | The tank holds 2.5 times the average daily design flow. For an individual home the flow is 250 gallons a day with one bedroom, 300 with two, 400 with three and 100 more for each additional bedroom. A one-bedroom home may use a 500 gallon tank. |
| Massachusetts | The tank holds twice the design flow and never less than 1,500 gallons. The design flow of a single-family home is 110 gallons a day per bedroom and at least 330, so twice the flow passes 1,500 gallons only at seven bedrooms (770 gallons a day). |
| Nebraska | Table 1 gives the design flow of a single-family home: 100 gallons a day plus 100 for each bedroom (one bedroom 200, two 300, three 400, four 500, five 600, six 700). Table 3 turns the flow into a tank for a home without a garbage disposal or a large tub: 200, 300 and 400 gallons a day, 1,000 gallons; 500, 1,250; 600, 1,500; 700, 1,750. |
| Pennsylvania | The rule sets a daily flow of 400 gallons for up to three bedrooms and 100 gallons more for each further bedroom, and a formula from flow to tank capacity: up to 500 gallons a day, 900 gallons plus 3.5 times the flow over 400; above that, 1,250 gallons plus 1.5 times the flow over 500. |
| Texas | Table III gives a daily usage rate by bedrooms and home size (one or two bedrooms under 1,500 sq ft: 225 gallons; three bedrooms under 2,500 sq ft: 300; four under 3,500: 375; five under 4,500: 450; six under 5,500: 525). Table II turns the rate into a tank: up to 250 gallons a day, 750 gallons; 251 to 350, 1,000; 351 to 500, 1,250; 501 to 1,000, 2.5 times the rate. |
| Vermont | The design flow is 70 gallons a day for each person: two persons in each of the first three bedrooms, one in each bedroom after that, and never fewer than two bedrooms for a single-family home (two bedrooms 280 gallons a day, three 420, four 490, five 560, six 630). Table 9-1 asks for 1,000 gallons up to a flow of 560 gallons a day and twice the flow above that. |
States with no statewide tank size
| State | Who sets the size |
|---|---|
| California | The statewide policy sets construction standards for septic tanks but no size by number of bedrooms. The county or city that issues the permit sets the size. |
| District of Columbia | The District's own regulations set no tank size by number of bedrooms. Its plumbing code is the 2015 International Plumbing Code with the District's amendments, and the amendments to the drainage chapter cover only sumps, ejectors and backwater valves. |
| Michigan | The state does not publish a tank size by number of bedrooms. The local health department that covers the home issues the permit under its own sanitary code and sets the size. |
| Wisconsin | The state code gives no tank size by number of bedrooms. The tank is sized in the plan of each system, which is reviewed before the permit is issued. The department's handbook for inspectors gives 2.088 times the design flow as the capacity for a three-year pumping cycle; with the code's design flow of 150 gallons a day per bedroom that is about 940 gallons for three bedrooms and 1,250 for four. |
The rule in each state
Where these numbers come from
Each size is from the state's own published regulation, read on October 8, 2026. The wording of each rule · Methodology