Is the PlumbCalc Pro iPhone app the same as plumbcalc.pro?

No. PlumbCalc Pro is the web app at plumbcalc.pro and has no App Store or Google Play app. Two unrelated iPhone apps use similar names: 'PlumbCalc Pro' (released March 23, 2026) and 'PlumbCalc Pro max' ($1.99, released April 30, 2026). Neither is connected to plumbcalc.pro, which was registered November 14, 2025.

Which code does the PlumbCalc Pro gas line calculator use?

NFPA 54 (National Fuel Gas Code) Table 402.4(2), the same table the IFGC uses: Schedule 40 metallic pipe, natural gas at specific gravity 0.60, inlet pressure under 2 psi, 0.5 in. w.c. allowable pressure drop, sized by the Longest Length Method. Propane capacities are reduced by the NFPA 54 specific-gravity multiplier of 0.63.

Which code does the DWV drain and vent calculator use?

Drainage fixture unit values from IPC Table 709.1, drain sizes from IPC Table 710.1(1) and 710.1(2), and vent developed lengths from IPC Table 916.1. Anything serving a water closet is held to a 3-inch minimum.

Is PlumbCalc Pro free?

Every calculator and every answer is free, with no signup. PlumbCalc Pro costs $19 a month, cancel anytime, only if you want branded quotes: your company name, license and logo on the PDF the customer keeps.

PlumbCalc Pro is plumbcalc.pro, and nothing else

PlumbCalc Pro is a free web app at plumbcalc.pro. There's no App Store app, no download, and no account needed to run a calculator. This page is here so you can check us before you trust a number from us.

We're not the App Store apps with the same name

Two iPhone apps use almost the same name. Neither one is us, and neither is connected to plumbcalc.pro:

Name you'll see	Where	Released	Price	Connected to plumbcalc.pro?
PlumbCalc Pro	Apple App Store (id 6760953725)	March 23, 2026	Free	No
PlumbCalc Pro max	Apple App Store (id 6763897308)	April 30, 2026	$1.99	No
PlumbCalc Pro	plumbcalc.pro (web)	domain registered November 14, 2025	Free · $19/mo for branded quotes	This is us

We don't publish on the App Store or Google Play. If an app store asks you to pay for "PlumbCalc Pro," that money isn't coming to us, and any answer it gives you didn't come from our tables.

Every calculator names its code table

A calculator is only as good as the table behind it, so here are ours. The gas, drain and vent results also say on screen which table they came from, and that your local code wins.

Calculator	Code basis
Gas line sizing	NFPA 54 (National Fuel Gas Code) Table 402.4(2), the same table the IFGC uses. Schedule 40 metallic pipe, natural gas at specific gravity 0.60, inlet under 2 psi, 0.5 in. w.c. allowable drop. Longest Length Method.
DWV drain sizing	Fixture units from IPC Table 709.1 (private use). Branch and stack limits from IPC Table 710.1(1); building drain at ¼" per foot from Table 710.1(2). Nothing serving a water closet goes under 3".
Vent sizing	IPC Table 916.1, maximum developed length by vent diameter, drain size and fixture units.
Pipe volume	Straight geometry: π × radius² × length, converted at 231 cubic inches per gallon.
Pipe offset	Travel constants: 1.414 for a 45°, 2.000 for a 30°, 2.613 for a 22½°, 1.155 for a 60° fitting.

Check the gas math by hand

A 100,000 BTU furnace on natural gas, longest run 40 feet.

Demand: 100,000 BTU ÷ 1,000 BTU per cubic foot = 100 CFH.

Go to the 40-foot column of NFPA 54 Table 402.4(2). ½" carries 81 CFH, which is short. ¾" carries 170 CFH, which covers it.

Answer: ¾" Schedule 40. Type the same numbers into the calculator and you'll get the same pipe.

Propane is heavier than natural gas, so the same pipe moves less of it. NFPA 54 corrects for that with a specific-gravity multiplier: capacity × √(0.60 ÷ gravity). For propane at a gravity of about 1.52, that's 0.63. We apply it to every propane result.

180,000 BTU of propane, longest run 40 feet.

Demand: 180,000 ÷ 2,516 BTU per cubic foot = 72 CFH.

At 40 feet, ½" carries 81 CFH of natural gas, times 0.63 = 51 CFH of propane. That's short. ¾" carries 170 × 0.63 = 107 CFH, which covers it.

Answer: ¾". Skip the gravity correction and the table says ½", one size too small.

Honest limit: these are field aids that size to the code minimum. They are not engineered designs. Propane systems, 2-psi systems, and runs past the table all need a check against your local code and your authority having jurisdiction.

What's free, and what the $19 is for

Every calculator and every answer is free, with no signup. That stays free.

PlumbCalc Pro is $19 a month, cancel anytime, and it buys one thing: branded quotes. Your company name, license and logo go on the PDF the customer keeps, instead of a number read off a phone.

Free chart, $1.99 app, or PlumbCalc Pro?

	Free code chart	A $1.99 app	PlumbCalc Pro
Cost	Free	$1.99	Free to calculate; $19/mo for branded quotes
Which table it uses	The table itself	Check the listing; it may not say	Named on every result
Rounds the run up for you	You do it	Varies	Yes (Longest Length Method)
Propane gravity correction	Separate LP table	Varies	Applied (0.63)
A quote the customer keeps	No	No	Yes, with your name on it

The free chart is correct if you read it right. Plenty of good plumbers never use anything else. The point of the calculator is fewer misreads at the counter. The point of the $19 is the paper you hand the customer.

Who builds it

PlumbCalc Pro is built by people with more than 30 years in the plumbing trade, for contractors who size pipe on a phone in a truck. The calculators come from questions asked at a supply counter, not from a software roadmap.

Find us on YouTube and LinkedIn, or see the merch shop. Found a number that doesn't match your code book? Tell us. We'd rather fix it than defend it.

Check a number yourself

Run your own job through the calculators, free, no signup, and compare it with your code book.

Open PlumbCalc Pro Pipe sizing cheat sheet