Guides/What a subscription costs
Rafter geometry has not changed since anyone reading this was born. Here is what renting the arithmetic comes to over the life of a tool belt — and the case for and against paying that way.
The clearest version of this argument is not ours. It is a review left on the App Store by someone who had been using the product for years:
"The subscription price of this app is nearly equivalent to buying a new calculator every year."
That is a tradesperson doing arithmetic about a company that sells calculators. It is worth taking seriously rather than dismissing, and it is worth checking.
Construction Master Pro Calc, from Calculated Industries, is listed on the App Store as a free download with subscription in-app purchases: $4.99 a month or $39.99 a year, with a free trial. The same company has sold physical Construction Master calculators as a one-time purchase since 1978.
We are also not going to tell you their app is bad. It is not. Forty-five years of refinement is in it, it is taught in trade schools, and its dimensional maths is the reason the name is close to generic on a jobsite. This page is about the billing model, which is a separate question from whether the tool is good.
Set the numbers to whatever you are actually looking at. The maths is plain multiplication — no discount rate, no inflation adjustment — because the point is a figure you can check on the back of a receipt.
A calculator outlasts most trucks. Ten years is not a stretch.
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Worth saying plainly, because the argument is worthless if it is just anti-subscription noise. Some software genuinely should be rented:
In each case you are funding work that continues after the purchase. That is fair, and a one-time price would be the dishonest option, because the app would quietly stop being maintained.
A construction calculator has none of those. The geometry has not changed. A 6/12 hip over a 144-inch run was exactly 216 inches when the Construction Master shipped in 1978 and it is exactly 216 inches now. There is no server, no live data feed, nothing running while the phone is in your pocket.
The honest counter-argument, which deserves stating: maintenance is a real cost. Operating systems change, screens change, bugs surface, and somebody has to keep the thing running on next year's phone. That work is genuine and it has to be paid for.
But it is amortisable into a purchase price — which the same company proves every time it sells a physical calculator once and supports it for a decade. Recurring maintenance does not require recurring billing. It requires pricing the purchase properly.
Not the money. It is that a calculator is a tool, and tools are things you own. A framing square bought in 1994 still works. A tape measure does not expire. The subscription model asks a trade whose entire relationship with tools is ownership to treat one of them as a rental — and to keep paying, or lose access to arithmetic that was settled before any of us turned up.
That is why the review above lands. It is not really about $39.99.
Being straight about this, because a page like this is worthless from someone hiding their own position.
If that ever changes, this page comes down first. Publishing this argument and then quietly moving to a subscription would deserve every screenshot it got.
In the meantime the twelve free calculators are the only claim we can actually back today — rafters, stringers, board feet, concrete, conduit offsets, rolling offsets, rebar, compound miter and the rest. Every formula is checked against a fixture with a hand-verified answer, and the page says how.
The Construction Master Pro Calc app on the App Store is a free download with subscription in-app purchases, listed at $4.99 a month or $39.99 a year, with a free trial. Calculated Industries also sells physical Construction Master calculators as a one-time purchase. Prices change, so check the store listing for the current figure.
At $39.99 a year, ten years is $399.90. Billed monthly at $4.99 it is $598.80, because twelve monthly payments come to $59.88 rather than $39.99. Against a one-time purchase of around $30, the subscription passes that price in roughly nine months on annual billing.
Because they carry ongoing costs: servers to run, data that has to stay current, or a service that keeps working on your behalf. A subscription funds work that continues after you buy. The question worth asking is whether the app you are paying for actually has those costs.
No. If an app maintains live data or runs a service for you, a subscription is the honest way to pay for it and a one-time price would mean the app eventually stops being maintained. The argument here is narrower: the geometry a construction calculator runs on does not change, so there is nothing ongoing to fund.
Check it against the job. Building codes, span tables and product specifications vary by jurisdiction and manufacturer. Your approved drawings and your local code govern, not this page.