About SizingKit

Nine sections, one trade or one kind of decision each. The catalog on the homepage lists every page with a line on what it works out, and the homepage itself carries a console that converts 23 quantities across 124 units.

• Electrical — 13 pages
• Power & current — 7 pages
• Electronics — 10 pages
• HVAC & refrigeration — 16 pages
• Pipe & pumps — 11 pages
• Machining — 12 pages
• Sheet metal & stock — 10 pages
• Mechanical — 9 pages
• Energy & cost — 9 pages

Every sourced number on this site was compiled 2026-09-05 and carries its own citation — not a bibliography at the bottom of the page, but the article or table number rendered beside the result that used it, where somebody checking the answer against a code book will look. These are the standards behind each family.

Conductors and raceway

NEC (NFPA 70) 2023 — Table 310.16 ampacities, 310.15(B)(1) and 310.15(C)(1) correction and adjustment, 240.4(D) small conductors, 240.6(A) standard device ratings, 250.122 grounding, Tables 430.248 and 430.250 motor full-load current, 430.52(C)(1) motor protection, and Chapter 9 Tables 1, 4 and 5 for fill. Conduit internal diameters trace back to ANSI C80.1, C80.3 and C80.6.

Air, heat and refrigerant

ASHRAE Handbook—Fundamentals for psychrometrics, duct friction and surface film resistances; ASHRAE 62.1 and 62.2 for ventilation rates; ACCA Manual J for design conditions and internal gains, Manual D for friction rate and Manual S for equipment selection limits.

Pipe, water and drainage

ASME B36.10M for steel pipe walls, ASTM B88 for copper tube, ASTM F876 and D2846 for PEX and CPVC, IPC 2021 Tables 604.4, 709.1, 710.1 and 704.1 for fixture flow, drainage fixture units, branch capacity and slope, and UPC 708.0 for the slope minimum where a jurisdiction adopted that code instead.

Drills, threads and fits

ANSI/ASME B94.11M for the fractional, number, letter and metric drill series and drill point angles; ASME B1.1 for Unified threads and ISO 261 and 724 for metric; ISO 286-1 and 286-2 for IT grades and shaft deviations; ISO 1302 for surface roughness grades.

Metals, fasteners and sheet

ASTM E140 for hardness conversion, ASTM A240 and AISI grade data for stainless densities, ASTM A36 and B209 for the tensile strengths behind bend tonnage, ASTM A6/A6M for mill weight tolerance, and SAE J429 with ISO 898-1 for fastener grades.

Where a standard defines a table by a formula, the table is generated from the formula rather than retyped. AWG diameters come out of d = 0.005 × 92^(36−n)/39, the gauge’s own definition, and the correction factors of NEC Table 310.15(B)(1) come out of the equation the table is derived from. A transcribed table can hold a typo that nobody notices for years; a generated one cannot hold one at all.

Every number that reaches a page here is marked as one of two kinds, and the difference is visible rather than editorial.

A fact is definitional, a code table, or a size somebody manufactures. An inch is 25.4 mm — exactly, by the international yard and pound agreement of 1959, not to some number of decimal places — and a pound is 0.45359237 kg the same way. Everything downstream of those two is arithmetic on them: the horsepower is 550 ft·lbf/s spelled out rather than 745.7 pasted in, and the psi and the BTU are computed the same way, so two constants that ought to agree cannot drift apart in the fourth digit. A figure like that is stated flat with its definition beside it, because nothing about your job changes it.

A default is a figure that genuinely moves, and the page hands it to you as a filled-in field rather than as a fact. The nut factor in a bolt torque calculation is the clearest one: torque is preload multiplied by diameter multiplied by K, and K is friction — around 0.20 for a plain dry steel fastener and around 0.15 once the threads are lubricated, which means applying a dry chart figure to an oiled bolt overloads it by roughly a third. So the field arrives prefilled, what moves it is printed beside it, and your fastener supplier’s own K wins the moment you type it. Presenting a figure like that as a fact would be the worst thing a page here could do, because it would look exactly as authoritative as the inch above it.

Most sizing questions are several limits competing, and returning only the winner hides the whole decision. A conductor is bounded by ampacity at its real ambient temperature, by the small-conductor rule, and by the voltage drop it can afford over the distance. Velocity fights pressure drop in a pipe. Tonnage fights die opening at a press brake. One of those is binding and the others have slack.

Naming the binding one turns a number into something you can act on. If the ampacity allowed a smaller conductor and the voltage drop is what forced the larger one, then shortening the run, splitting the load or accepting a different drop budget are all real options — and if ampacity was binding, none of them are. It is also the sentence that settles an argument on site, which is why it appears next to the answer rather than in a note underneath.

Nothing here is carried past the end of the data it came from. Some real examples: the approximate tensile column of the hardness tables is blank above 50 HRC and the Brinell column is blank at 68 HRC, because a standard Brinell ball cannot measure a material that hard and inventing a figure would only make the page look complete. Two cells of the three-phase motor full-load table are deliberately empty where the value could not be confirmed. The refrigerant pressure-temperature data is anchored every 20 °F from 0 to 140 °F and interpolated between those anchors — the page says so, and outside that span it returns nothing rather than a plausible extension of the curve.

The same rule covers whole tables this site does not reproduce. Design temperatures for specific cities are thousands of stations that get revised with each Handbook edition, so the pages that need one tell you where to look yours up instead of shipping a list that is wrong somewhere. A septic drain field’s soil loading rate varies eightfold across ordinary soils and legally comes from the perc test, so there is no default for it. Where a page needs a number this site does not hold, it says what the table is, that we do not reproduce it, and what to read — which is more useful than a number that cannot be checked.

1. Issue a verdict a code governs. These pages report what a table says and show the arithmetic on it. They never render “this is safe” or “this passes”, because compliance is decided by the edition your jurisdiction adopted, the amendments it made to that edition, and the inspector standing in front of the work. Two adjacent counties can read the same installation differently, and a web page has no way to know which one you are in.
2. Stand in for a stamped design. A service load calculation, a beam, a Manual J and a fault current study all end with a professional’s seal on them. What that seal buys is not arithmetic — it is somebody who has seen the building, carries the liability and is accountable for the assumptions. This site gets the numbers right up to that point and then says plainly that the point has been reached.
3. Replace a manufacturer’s own data for their own equipment. A target superheat for a fixed-orifice system, a pump’s NPSH required, a tooling maker’s chip load, an air handler’s blower curve: these are properties of one product, published by the people who built it and measured on it. A generic table would be an average of things that are not alike. Where a page touches one of these, it names the plate, the curve or the catalog as the authority and treats its own figure as the starting point.

There is also no price list anywhere on this site, no regional cost average and no “typical” installation. The energy and cost pages take the tariff from you because a rate that is right in one utility territory is wrong in the next one and stale within a season, and a published one would make the arithmetic look more authoritative while making the answer less true.

All of it stays in the browser. Loads, lengths, nameplate ratings, gauge readings and the tariff your utility charges are multiplied in the tab and forgotten on reload — nothing is uploaded, logged or kept, and there is no account to attach any of it to. That is also why the pages keep working in a mechanical room with no signal once they have loaded.

This describes what SizingKit itself does. It says nothing about what a browser extension, a corporate proxy or the machine in front of you might see — only that this site adds nothing to that list.