Run the number.
Get the verdict.
It holds up.
Code-accurate calculators for HVAC and electrical: superheat, R-454B, wire size, voltage drop. Every number the calculators compute is cited to its source, from NEC 2023 tables to published refrigerant data. Free, offline, no login.
The yellow book behind the truck seat, reborn as an app.
Together they re-derive our calculators' numbers from locked source modules and check them against the code sections, manufacturer charts, and federal rules they cite (and the structure of those tables). Use any tool here and the number you get was checked against its source first. This count is live, not a number we typed. Our own gate, and we say so.
what this counts
Every time we update the site, our build re-derives each calculator value from a locked source module and checks it against the exact thing it cites: the NEC 2023 section, the manufacturer chart, or the federal rule. This is our own deterministic gate, not a third-party audit. It does not make any single answer infallible. It means the math in front of you was checked against its sources before it reached you, and every number links to the source so you can check it yourself.
Most used on the job
Superheat & Subcooling Calculator
Check refrigerant charge with PT interpolation for R-454B, R-32, R-410A, and 7 more. Four-quadrant diagnostics tell you what the numbers mean.
R-454B readyNew · Meet Jim, your pocket assistantConduit Bending Calculator
Offsets, rolling offsets, 3- and 4-point saddles, stub-90s, back-to-back 90s, and kick-90s, with interactive bend diagrams and shrink tables.
New · Bends in Upscaled 3DVoltage Drop Calculator
Voltage drop for any run, plus reverse-solve for the minimum wire size that meets NEC recommendations. Tells you if the run passes or needs a bigger conductor.
NEC 2023EV Charger Install Calculator
Wire, breaker, and panel sizing for Level 2 charger installs per NEC 625, with GFCI requirements and a parts list. Flags whether your panel can carry it.
NEC 625Nobody finishes a job with one answer.
You searched one question. The job behind it has ten. Intry carries the whole chain.
The question
“Wire size for a 50A EV charger.” Answered cold: #6 copper, cited to NEC Table 310.16, verdict on top.
The job behind it
That wire lives in a job: the panel that carries it, the breaker, the drop on a 120 ft run. Run each number here, and every reading stacks into the job.
The next move
One tap ships the whole job to your AI assistant, and it comes back with the next steps in order.
Every number a calculator computes stays cited to the source it came from. The plan is the assistant's take.
More calculators
Wire Size Calculator
NEC 310.16 ampacity with temp derating and bundling.
Conduit Fill Calculator
NEC Chapter 9 fill for EMT, IMC, RMC, PVC, and ENT.
Box Fill Calculator
Junction box fill per NEC 314.16.
BTU Load Calculator
Cooling and heating load by climate zone, room-by-room.
Wire Size for Appliances
Breaker and wire for a dryer, range, water heater, hot tub, AC, pump, and more, from the NEC tables.
What Size AC Do I Need?
AC size by room or whole house from the ENERGY STAR table and climate zone, with tonnage.
What Intry is
Intry is the verified engine for the trades, and the field tool that carries the whole job. The number is where most calculators stop; Intry reads it back as a verdict, what it means and the next move. From there the whole call travels with you: Jim, the assistant wired into the same verified engines, works the job through; each reading builds a record of that unit, so a second visit shows what changed; and one tap hands your customer a cited report. It is the same engine your AI assistant can run through the MCP endpoint, computed and cited, never guessed. Built for HVAC and electrical through the R-454B and A2L transition.
Is Intry accurate?
Every number our calculators compute comes from a locked source module, not hand-typed, and a deterministic test re-derives and source-checks the numbers on every deploy. This is the Intry Verified standard, our own gate, not a third-party audit.
Which NEC edition does Intry use?
The NEC 2023 edition, with the specific article and table cited on every electrical calculation (for example 310.16 ampacity, 250.122 grounding, Chapter 9 conduit fill). The 2023 to 2026 changes are tracked on their own page.
Is Intry free?
Yes. Every calculator is free, with no login, no paywall, and no sign-up. Intry also installs to your phone as an app and works offline in the field.
Can my AI assistant run Intry's calculators?
Yes. Intry publishes a Model Context Protocol (MCP) endpoint, so an AI assistant you connect can run the calculators directly and get back the same cited number, a structured readout, and the source it was computed from (plus a verdict where the reading calls for one), rather than quoting a static page. Setup is at intrysys.com/mcp.
Built for the field, not the office.
Every calculator shows the math and cites its source: NEC table numbers, refrigerant PT data, manufacturer specs. Get your answer at the panel or the condenser in seconds. And when the job runs deeper than one question, hand the whole thing off, and it comes back with the plan.
No login. No paywall. No spam.