Welcome to our Septic Tank Size Calculator! This handy tool allows you to estimate your septic system’s ideal tank volume and capacity. Whether you’re planning for a residential property or need to upgrade an existing system, our calculator considers factors like the number of bedrooms, water usage, and retention time. Say goodbye to guesswork and hello to accurate septic tank sizing tailored to your needs. Get started now and ensure a well-designed and efficient septic solution for your property.

## What is a septic tank size calculator?

A septic tank size calculator is a tool used to estimate the appropriate dimensions and capacity of a septic tank based on various factors such as the number of occupants in a household, the daily wastewater flow rate, and the type of soil in the area. A septic tank is a vital component of a septic system, which is a decentralized wastewater treatment system commonly used in rural and suburban areas where centralized sewage treatment is not available.

The calculator takes into account the specific needs of a property to determine the size of the septic tank that can effectively handle the wastewater generated by the occupants. It considers factors like water usage, occupancy, and local regulations to provide an estimate of the required tank volume. This helps ensure that the septic system operates efficiently and avoids issues such as overflows, backups, or premature maintenance.

The septic tank size calculator usually involves inputting information such as the number of bedrooms in a house, the average water usage, and the type of septic tank system (conventional, aerobic, etc.). Based on this data, the calculator uses standard formulas and guidelines to suggest an appropriate tank size that can handle the wastewater load and provide proper treatment.

It’s important to note that a septic tank size calculator provides an estimate and should be used as a starting point. Local regulations, soil conditions, and other factors can influence the final septic system design. Therefore, working with a professional, such as a septic system designer or engineer, is recommended to ensure that the septic tank size and entire system are appropriately designed for the specific property and its wastewater needs.

## How does this septic tank size calculator work?

Imagine you have a special tool, like a virtual calculator, to help you figure out how big your septic tank should be. This calculator considers different septic tank shapes and helps you find the right size for your home.

### Here’s how it works step by step:

**Choose Your Tank Type:**A drop-down list is at the top of the calculator. It’s like a menu where you can choose the shape of your septic tank. You’ll see options like “Horizontal Cylinder,” “Vertical Cylinder,” “Rectangle,” and others. Just pick the one that matches your tank.**Enter Tank Details:**Once you’ve selected your tank shape, the calculator will show you a set of empty boxes below. It’s like giving you a space to enter some numbers. The numbers you need to enter depend on your tank’s shape. For example, if you picked “Horizontal Cylinder,” you’ll need to type in the circle’s radius (half the width) of the circle and the length of the tank.**Hit the Calculate Button:**After you’ve entered the numbers, there’s a big button that says “Calculate.” It’s like pressing a magic button to make the calculator do its thing.**See the Results:**Right under the “Calculate” button, you’ll see some information pop up. It will tell you two important things: the volume of your septic tank (how much space it has inside) and an approximate amount of liquid it can hold. This liquid is the wastewater from your home, and the calculator tells you roughly how much your tank can handle.**What the Numbers Mean:**The volume measures the space inside your tank. The bigger the volume, the larger your tank needs to be. The “approximate liquid holding capacity” is like telling you how much wastewater your tank can hold. This helps you understand if the tank is the right size for your family’s needs.

## Formulas for calculating the volume/size of various types of septic tanks

Here’s a table with the formulas for calculating the volume/size of various types of septic tanks:

Septic Tank Type | Shape | Formula for Volume |
---|---|---|

Horizontal Cylinder | Cylinder | V = π * r^2 * L |

Vertical Cylinder | Cylinder | V = π * r^2 * H |

Rectangle | Rectangular Prism | V = l * w * h |

Horizontal Oval | Elliptical Cylinder | V = π * a * b * L |

Vertical Oval | Elliptical Cylinder | V = π * a * b * H |

Horizontal Capsule | Capsule | V = π/6 * (3 * r^2 * L + d^2 * L) |

Vertical Capsule | Capsule | V = π/6 * (3 * r^2 * H + d^2 * H) |

In the above formulas:

- π represents the mathematical constant pi (approximately 3.14159).
- r is the radius of the circular base (or the minor radius for oval shapes).
- L is the length of the tank (or the height for vertical tanks).
- H is the height of the tank (or the length for vertical tanks).
- a and b are the semi-major and semi-minor axes of the elliptical base.
- l, w, and h are the rectangular tank’s length, width, and height.
- d is the diameter of the spherical ends of capsule tanks.

## Examples of the volume and the liquid holding capacity of different types of septic tanks

Septic Tank Type | Shape | Dimensions (meters) | Volume (units³) | Approx. Liquid Holding Capacity (liters) |
---|---|---|---|---|

Horizontal Cylinder | Cylinder | Radius: 1, Length: 3 | 9.42 | 9,420 |

Vertical Cylinder | Cylinder | Radius: 0.75, Height: 4 | 7.07 | 7,070 |

Rectangle | Rectangular Prism | Length: 2, Width: 1, Height: 1 | 2.00 | 2,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 2, Semi-Minor Axis: 1, Length: 3 | 18.85 | 18,850 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 1.5, Semi-Minor Axis: 1, Height: 2 | 9.42 | 9,420 |

Horizontal Capsule | Capsule | Radius: 1, Diameter: 2, Length: 4 | 11.79 | 11,790 |

Vertical Capsule | Capsule | Radius: 0.8, Diameter: 1.6, Height: 3 | 5.87 | 5,870 |

Horizontal Cylinder | Cylinder | Radius: 1.5, Length: 5 | 35.34 | 35,340 |

Vertical Cylinder | Cylinder | Radius: 1.2, Height: 6 | 27.09 | 27,090 |

Rectangle | Rectangular Prism | Length: 3, Width: 2, Height: 1.5 | 9.00 | 9,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 2.5, Semi-Minor Axis: 1.5, Length: 4 | 47.12 | 47,120 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 2, Semi-Minor Axis: 1.2, Height: 2.5 | 18.85 | 18,850 |

Horizontal Capsule | Capsule | Radius: 1.2, Diameter: 2.4, Length: 5 | 25.46 | 25,460 |

Vertical Capsule | Capsule | Radius: 1, Diameter: 2, Height: 4 | 16.61 | 16,610 |

Horizontal Cylinder | Cylinder | Radius: 2, Length: 6 | 75.40 | 75,400 |

Vertical Cylinder | Cylinder | Radius: 1.5, Height: 8 | 56.55 | 56,550 |

Rectangle | Rectangular Prism | Length: 4, Width: 2, Height: 2 | 16.00 | 16,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 3, Semi-Minor Axis: 2, Length: 5 | 94.25 | 94,250 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 2.5, Semi-Minor Axis: 1.8, Height: 3 | 42.39 | 42,390 |

Horizontal Capsule | Capsule | Radius: 1.5, Diameter: 3, Length: 6 | 42.41 | 42,410 |

Vertical Capsule | Capsule | Radius: 1.2, Diameter: 2.8, Height: 5 | 29.11 | 29,110 |

Horizontal Cylinder | Cylinder | Radius: 2.5, Length: 7 | 137.80 | 137,800 |

Vertical Cylinder | Cylinder | Radius: 2, Height: 10 | 125.66 | 125,660 |

Rectangle | Rectangular Prism | Length: 5, Width: 3, Height: 2 | 30.00 | 30,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 4, Semi-Minor Axis: 2.5, Length: 6 | 188.50 | 188,500 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 3.5, Semi-Minor Axis: 2, Height: 4 | 88.36 | 88,360 |

Horizontal Capsule | Capsule | Radius: 2, Diameter: 4, Length: 7 | 79.64 | 79,640 |

Vertical Capsule | Capsule | Radius: 1.8, Diameter: 3.6, Height: 6 | 58.65 | 58,650 |

Horizontal Cylinder | Cylinder | Radius: 3, Length: 8 | 226.20 | 226,200 |

Vertical Cylinder | Cylinder | Radius: 2.5, Height: 12 | 294.52 | 294,520 |

Rectangle | Rectangular Prism | Length: 6, Width: 4, Height: 3 | 72.00 | 72,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 5, Semi-Minor Axis: 3, Length: 7 | 330.82 | 330,820 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 4, Semi-Minor Axis: 2.5, Height: 5 | 132.73 | 132,730 |

Horizontal Capsule | Capsule | Radius: 2.5, Diameter: 5, Length: 8 | 141.37 | 141,370 |

Vertical Capsule | Capsule | Radius: 2, Diameter: 4.5, Height: 7 | 100.17 | 100,170 |

Horizontal Cylinder | Cylinder | Radius: 3.5, Length: 9 | 381.71 | 381,710 |

Vertical Cylinder | Cylinder | Radius: 3, Height: 14 | 792.39 | 792,390 |

Rectangle | Rectangular Prism | Length: 7, Width: 5, Height: 4 | 140.00 | 140,000 |

Horizontal Oval | Elliptical Cylinder | Semi-Major Axis: 6, Semi-Minor Axis: 4, Length: 8 | 452.38 | 452,380 |

Vertical Oval | Elliptical Cylinder | Semi-Major Axis: 5.5, Semi-Minor Axis: 3.5, Height: 6 | 207.81 | 207,810 |

Horizontal Capsule | Capsule | Radius: 3, Diameter: 6, Length: 9 | 283.53 | 283,530 |

Vertical Capsule | Capsule | Radius: 2.5, Diameter: 5.5, Height: 8 | 180.59 | 180,590 |

## How do you calculate septic tank capacity per person?

To calculate septic tank capacity per person, you can use the estimated range of water usage per person and consider the recommended retention time for wastewater treatment. Here’s a step-by-step process:

**Determine Average Water Usage:**Start by considering the estimated range of water usage per person. In the U.S., experts estimate that occupants use between 50 and 100 gallons of water per person daily.**Choose a Retention Time:**The retention time is when wastewater remains in the septic tank for treatment. A common retention time is 24 to 48 hours. Choose a specific value within this range.**Calculate Daily Flow:**Multiply the estimated water usage per person by the number of occupants in your household. This will give you the total daily wastewater flow into the septic tank. Daily Flow (in gallons) = Estimated Water Usage per Person (in gallons/person/day) × Number of Occupants**Calculate Tank Volume:**Use the chosen retention time to calculate the required septic tank volume. The formula is: Tank Volume (in gallons) = Daily Flow (in gallons) × Retention Time (in days)**Adjust for Peak Load:**To accommodate peak water usage, you can increase the calculated tank volume by a certain percentage (e.g., 25%).Adjusted Tank Volume (in gallons) = Tank Volume (in gallons) × (1 + Peak Load Percentage)**Check Local Regulations:**Be sure to check with local health departments or regulations for specific requirements or guidelines for septic tank sizing in your area.

### Here’s an example calculation:

Let’s say you have a household of 4 people and choose a retention time of 48 hours. The estimated water usage per person is 75 gallons. You want to account for a 25% peak load increase.

- Daily Flow = 75 gallons/person/day × 4 people = 300 gallons/day
- Tank Volume = 300 gallons/day × 2 days = 600 gallons
- Adjusted Tank Volume = 600 gallons × (1 + 0.25) = 750 gallons

In this example, you would need a septic tank with a capacity of approximately 750 gallons to effectively handle the wastewater generated by 4 people with an estimated water usage of 75 gallons per person per day.

## What is normal septic tank capacity?

The normal septic tank capacity can vary based on factors such as the number of users, frequency of sludge removal, and local regulations. However, as a general guideline, the capacity of a septic tank is often determined by considering the estimated water usage per person and the recommended retention time for wastewater treatment.

As you mentioned, the liquid capacity of a septic tank is often estimated to be around 130 to 70 litres per person. This means that the tank is designed to hold a certain amount of liquid waste for every person using the septic system.

For example, if we take the range you provided:

**Liquid Capacity Per Person:**70 to 130 litres

If we assume an average value within this range, such as 100 litres per person, and consider a retention time of 2 days (48 hours), we can calculate the approximate septic tank capacity for a household with a certain number of users.

Let’s do an example calculation:

Suppose you have a household of 4 people and use an average liquid capacity of 100 liters per person.

**Daily Flow:**4 people × 100 liters/person = 400 liters/day**Tank Volume:**400 liters/day × 2 days = 800 liters

So, for a household of 4 people with an estimated liquid capacity of 100 liters per person, you would need a septic tank of approximately 800 liters.

## How do you calculate septic tanks in liters?

Calculating septic tank capacity in liters involves considering the estimated water usage per person and the recommended retention time for wastewater treatment. Here’s a step-by-step process:

**Determine Average Water Usage:**Start by considering the estimated water usage per person. This can vary based on factors like geography, lifestyle, and water conservation practices. A common range is 70 to 130 liters per person per day.**Choose a Retention Time:**The retention time is when wastewater remains in the septic tank for treatment. A common retention time is 2 to 3 days. Choose a specific value within this range.**Calculate Daily Flow:**Multiply the estimated water usage per person by the number of occupants in your household. This will give you the total daily wastewater flow into the septic tank.Daily Flow (in liters) = Estimated Water Usage per Person (in liters/person/day) × Number of Occupants**Calculate Tank Volume:**Use the chosen retention time to calculate the required septic tank volume. The formula is:Tank Volume (in liters) = Daily Flow (in liters) × Retention Time (in days)**Adjust for Peak Load:**To accommodate peak water usage, you can increase the calculated tank volume by a certain percentage (e.g., 25%).Adjusted Tank Volume (in liters) = Tank Volume (in liters) × (1 + Peak Load Percentage)**Check Local Regulations:**Be sure to check with local health departments or regulations for any specific requirements or guidelines for septic tank sizing in your area.

### Here’s an example calculation:

Let’s say you have a household of 4 people and you choose a retention time of 2 days. The estimated water usage per person is 100 liters. You want to account for a 25% peak load increase.

- Daily Flow = 100 liters/person/day × 4 people = 400 liters/day
- Tank Volume = 400 liters/day × 2 days = 800 liters
- Adjusted Tank Volume = 800 liters × (1 + 0.25) = 1000 liters

In this example, you would need a septic tank with a capacity of approximately 1000 liters to effectively handle the wastewater generated by 4 people with an estimated water usage of 100 liters per person per day.

## Minimum Septic Tank Capacity Table

See the following table for details on **Minimum Septic Tank Capacity** based on the number of residential bedrooms:

Number of Bedrooms | Minimum Septic Tank Size (Gallons) | Minimum Liquid Surface Area (Sq. Ft.) | Drainfield Size (Sq. Ft.) |
---|---|---|---|

2 or less | 1000 – 1500 | 27 | 800 – 2500 |

3 | 1000 – 2000 | 27 | 1000 – 2880 |

4 | 1250 – 2500 | 34 | 1200 – 3200 |

5 | 1500 – 3000 | 40 | 1600 – 3400 |

6 | 1750 – 3500 | 47 | 2000 – 3800 |

7 | 2000 – 4000 | 54 | 2400 – 4200 |

8 | 2250 – 4500 | 61 | 2800 – 4600 |