How do you clock a gas meter?

Shut off all other gas appliances, run the appliance you're testing, and time one full revolution of a known test dial (1 or 2 ft³) with a stopwatch. Cubic feet per hour = (3600 ÷ seconds per revolution) × dial size. Multiply CFH by the gas heating value to get BTU/h input.

What heating value should I use for natural gas?

Natural gas is commonly around 1,000–1,050 BTU per cubic foot, with 1,050 a frequent default. The exact value varies by region and gas composition — your local utility can give you the precise heating value for the most accurate result.

Does clocking the meter measure efficiency?

No. Clocking measures the actual fuel input (firing rate). Efficiency would be the BTU output divided by this input. To get output you'd measure the temperature rise and airflow. Compare the clocked input to the furnace nameplate input to spot an over- or under-fired unit.

How long should the test take?

Aim for a revolution time of about 30–120 seconds. Very short times (under ~15 seconds) amplify stopwatch error; very long ones get tedious. A 2 ft³ dial gives a longer, more accurate timing on high-input appliances.

Gas Meter Clocking Calculator

Free gas meter clocking calculator. Time one dial revolution to find a furnace or appliance's actual BTU/h input and cubic feet per hour, with adjustable gas heating value.

How gas meter clocking works

Clocking the meter measures an appliance’s actual gas input by timing how fast it burns a known volume of gas:

CFH = (3600 ÷ seconds per revolution) × test dial size (ft³)

BTU/h input = CFH × gas heating value (BTU/ft³)

The 3600 converts seconds to an hour. Natural gas runs about 1,000–1,050 BTU/ft³ (1,050 is a common default) — your utility can give the exact value, which is editable above.

Worked example

A furnace turns a 1 ft³ test dial in 42 seconds on natural gas at 1,050 BTU/ft³:

CFH = (3600 ÷ 42) × 1 = 85.7 ft³/h
BTU/h = 85.7 × 1,050 ≈ 90,000 BTU/h input

Compare that to the nameplate input to confirm the furnace is firing correctly.

Procedure notes

Isolate the appliance — shut off all other gas loads so only the test unit is drawing gas.
Time 30–120 seconds for accuracy; use a 2 ft³ dial on high-input appliances for a longer, steadier read.
This measures input only, not efficiency. To get output, pair it with the Furnace Temperature Rise Calculator (output = input × efficiency).

Safety first. Work on gas-fired equipment only within your training and local codes. Always check for leaks and proper combustion after any gas work.

How FieldPad helps in the field

Clock the meter here, then record the firing rate in FieldPad against the equipment and the job. Note an over- or under-fired furnace, attach it to the service record, and turn the correction into a documented estimate — offline, on your iPhone.

Gas Meter Clocking Calculator

How gas meter clocking works

Worked example

Procedure notes

How FieldPad helps in the field

Stop Re-Running These Numbers by Hand

Related Tools

Furnace Temperature Rise & Airflow Calculator