Transparent by default
Size your septic system with numbers you can check.
Every result shows the formula and the public standard behind it. No black boxes — just field instruments for tank size, perc rate, drain field, cost, and service.
SHOWS THE FORMULACITES THE STANDARDMOBILE-FIRST
Browse the calculators ↓ Tank size — try itLIVE
Five instruments · one method
Pick your calculator
Each one leads with the answer, then shows the math and the standard it cites.
Sizing
Septic tank size
Bedrooms → recommended minimum tank in gallons.
Open →Soil & Perc
Perc rate test
Drop time → soil class and design loading rate.
Open →
Sizing
Drain field size
Home + perc rate → absorption area and trench layout.
Open →Cost
System cost
System type → itemized installed-cost range.
Open →Maintenance
Pump-out schedule
Tank + household → years between pump-outs.
Open →The method
How every number is derived
See the formulas and the codes they come from.
Read the standard →No black boxes
Every result shows its work
01
The formula
The exact equation driving the readout — never hidden.
tank ≥ BR × 150 × 2
02
The public standard
The code or design manual the math is drawn from.
EPA 625/R-00/008
03
The itemized math
Each step totaled line by line, so you can check it.
600 gpd → 1,250 gal