Gas Rate Calculator Chart

Gas Rate Calculator & Reference Chart (BTU/hr Input)

Accurately determining the gas flow rate to an appliance—known as "clocking the meter"—is a critical procedure for HVAC technicians and gas engineers. It ensures that a furnace, boiler, or water heater is firing close to its rated input capacity as specified on the manufacturer's nameplate. Under-firing results in inefficiency and poor performance, while over-firing can cause overheating, equipment damage, and dangerous safety issues.

This calculator helps you quickly determine the BTU per hour input by timing a test dial on the gas meter. Below the calculator, you will also find a standard reference chart for common dial sizes and times.

Gas Appliance Rate Calculator

Ensure all other gas appliances are turned off before timing the meter.

0.5 ft³ dial 1 ft³ dial 2 ft³ dial 5 ft³ dial 10 ft³ dial

Default is approx. for Natural Gas. Use ~2500 for Propane.

function calculateGasRate() { var dialSizeInput = document.getElementById('dialSize').value; var secondsTakenInput = document.getElementById('secondsTaken').value; var calorificValueInput = document.getElementById('calorificValue').value; var dialSize = parseFloat(dialSizeInput); var seconds = parseFloat(secondsTakenInput); var cv = parseFloat(calorificValueInput); if (isNaN(dialSize) || isNaN(seconds) || isNaN(cv) || seconds <= 0 || dialSize <= 0 || cv <= 0) { document.getElementById('gasRateResult').innerHTML = "Please enter valid positive measurements."; return; } // Formula: BTU/hr = (Cubic Feet measured * Calorific Value * 3600 seconds/hr) / Seconds taken var btuPerHour = (dialSize * cv * 3600) / seconds; // Round to nearest whole number for practicality var roundedBtu = Math.round(btuPerHour); // Format output with commas for readability var formattedOutput = roundedBtu.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ","); document.getElementById('gasRateResult').innerHTML = "Estimated Input: " + formattedOutput + " BTU/hr"; }

How to Perform the Calculation

1. Identify the test dial on the gas meter. It is usually marked with a volume, such as "1/2 Cubic Foot," "1 Cubic Foot," or "2 Cubic Feet" per revolution.
2. Turn off all other gas appliances in the building (stoves, dryers, fireplaces).
3. Turn up the thermostat for the appliance you are testing so it fires at maximum capacity.
4. Using a stopwatch, time exactly how many seconds it takes for the chosen dial to complete one full revolution.
5. Enter the dial size, the time in seconds, and the local calorific value of the gas (usually obtained from the utility provider) into the calculator above.
6. Compare the result with the appliance's rating plate. An acceptable variance is typically within +/- 5%.

Quick Reference Gas Rate Chart (Natural Gas @ 1030 BTU/ft³)

This chart provides quick estimates for standard natural gas inputs based on timing a **1 cubic foot** test dial.

Time (Seconds for 1 ft³ dial)	Approximate BTU/hr Input
30	123,600
36	103,000
40	92,700
45	82,400
50	74,160
60 (1 min)	61,800
72	51,500
90 (1.5 min)	41,200
120 (2 min)	30,900

Note: Chart values are based on a calorific value of 1030 BTU per cubic foot. Actual local gas values may vary slightly.