Twelve free tools · no sign-up
Septic and drainage math, worked out before you dig
Gravel volumes, pipe slope, tank capacity, trench and excavation quantities. Enter your measurements in feet, inches or metric and every calculator shows its arithmetic, so you can check the answer instead of trusting it.
12 calculators
- septicSeptic Tank VolumeConvert the inside dimensions of a rectangular or cylindrical tank into gallons, liters and cubic feet.
- septicDaily WastewaterMultiply occupants by an editable gallons-per-person-per-day figure to see daily, weekly and annual flow.
- septicPerc RateConvert an observed water-level drop and elapsed time into minutes per inch and inches per hour.
- septicDrain Field AreaDivide a daily design flow by a soil loading rate you supply to get a rough absorption area in square feet.
- drainageFrench Drain GravelWork out the gravel volume for a French drain trench, with the perforated pipe subtracted and a waste allowance added.
- drainagePipe SlopeTurn a measured run and vertical drop into slope percentage, fall per foot and a 1-in-X ratio.
- drainagePipe DropEnter a pipe length and a target slope to get the total fall you need to set between both ends.
- drainageDrainage StoneVolume and tonnage for a rectangular bed of drainage stone, with an editable density and waste allowance.
- drainageRainfall RunoffEstimate how much water a roof, driveway or lawn sheds during a given rainfall, in gallons and cubic meters.
- earthworkTrench VolumeLength, width and depth to cubic feet, cubic yards and cubic meters for any straight trench.
- earthworkExcavation VolumeIn-place and loose volumes for a rectangular or circular dig, including a swell allowance for hauling.
- earthworkSoil WeightTurn a soil or aggregate volume into pounds, US tons and kilograms using an editable material density.
Most used
Browse all twelve- French Drain Gravel CalculatorWork out the gravel volume for a French drain trench, with the perforated pipe subtracted and a waste allowance added.Open calculator
- Drain Pipe Slope CalculatorTurn a measured run and vertical drop into slope percentage, fall per foot and a 1-in-X ratio.Open calculator
- Septic Tank Volume CalculatorConvert the inside dimensions of a rectangular or cylindrical tank into gallons, liters and cubic feet.Open calculator
- Trench Volume CalculatorLength, width and depth to cubic feet, cubic yards and cubic meters for any straight trench.Open calculator
- Drainage Stone CalculatorVolume and tonnage for a rectangular bed of drainage stone, with an editable density and waste allowance.Open calculator
- Excavation Volume CalculatorIn-place and loose volumes for a rectangular or circular dig, including a swell allowance for hauling.Open calculator
Septic calculators
Tank capacity, household flow, percolation timing and absorption area estimates.
- Septic Tank Volume CalculatorConvert the inside dimensions of a rectangular or cylindrical tank into gallons, liters and cubic feet.
- Daily Wastewater CalculatorMultiply occupants by an editable gallons-per-person-per-day figure to see daily, weekly and annual flow.
- Perc Rate CalculatorConvert an observed water-level drop and elapsed time into minutes per inch and inches per hour.
- Drain Field Area EstimatorDivide a daily design flow by a soil loading rate you supply to get a rough absorption area in square feet.
Drainage calculators
French drains, pipe grade, stone quantities and runoff volumes.
- French Drain Gravel CalculatorWork out the gravel volume for a French drain trench, with the perforated pipe subtracted and a waste allowance added.
- Drain Pipe Slope CalculatorTurn a measured run and vertical drop into slope percentage, fall per foot and a 1-in-X ratio.
- Pipe Drop CalculatorEnter a pipe length and a target slope to get the total fall you need to set between both ends.
- Drainage Stone CalculatorVolume and tonnage for a rectangular bed of drainage stone, with an editable density and waste allowance.
- Rainfall Runoff CalculatorEstimate how much water a roof, driveway or lawn sheds during a given rainfall, in gallons and cubic meters.
Earthwork calculators
Trench and excavation volumes plus soil and aggregate weights.
- Trench Volume CalculatorLength, width and depth to cubic feet, cubic yards and cubic meters for any straight trench.
- Excavation Volume CalculatorIn-place and loose volumes for a rectangular or circular dig, including a swell allowance for hauling.
- Soil Weight CalculatorTurn a soil or aggregate volume into pounds, US tons and kilograms using an editable material density.
How these calculators work
Everything runs in your browser
No account, no upload, no server round trip. Your measurements never leave the page.
Units convert for you
Enter a length in feet and a width in inches. Each field carries its own unit and the conversion happens before the math.
The working is shown
Every result opens up into the steps behind it, so you can check the arithmetic against your own numbers.