Grease Trap Size Calculator
Plug in your kitchen’s peak meals per hour and the fixture flow rate; the tool returns the minimum trap capacity (in gallons) that most plumbing codes and county FOG programs will accept.
Enter your sink dimensions (inches) to calculate capacity and flow rate. Add multiple sinks to estimate combined demand for a single grease interceptor.
Multiple Sinks
Interceptor loading rule: 100% of largest + 50% of 2nd largest + 25% of each additional sink.
How the Calculator Functions
Every plumbing code begins with a simple requirement: size your interceptor so it can hold enough wastewater to trap fats, oils, and grease before they hit the sewer.
This calculator automates that math—enter the busiest hour’s meal count and your sink’s waste-flow rate (0.5 gpm is typical for a three-compartment sink), and the tool multiplies peak meals by flow, a 30-minute retention time, and a 0.75 load factor, then rounds up to the next whole gallon.
The result is the minimum trap capacity plan reviewers expect to see; if the number falls between standard sizes, choose the next larger model to sail through permitting on the first submission.
Can’t Find a Link?
Email info@greaseconnections.com with your county or request—our emergency response team will add the resource within one business day.
Last checked 17 May 2025 — next review Aug 2025