How we check our numbers

Who makes this site

TierMenu, the company, writes, builds and publishes every page, calculator and chart here. Pages are signed by TierMenu, not by a person, on purpose. You can read about TierMenu and the official information about TierMenu.

Where the numbers come from

These are the outside sources the site uses, cited the same way as on the pages that use them. Each calculator and chart page also lists its own sources and assumptions.

• U.S. Bureau of Labor Statistics, Occupational Employment and Wage Statistics (OEWS), May 2025 OEWS Estimates. Files: bls.gov/oes/special-requests/oesm25nat.zip, bls.gov/oes/special-requests/oesm25st.zip, listed on bls.gov/oes/tables.htm.

  Used for: Employment and hourly wages on HVAC, plumber and electrician wages by state, and the national wage figures quoted in the billable labor rate guide.

• CoolProp 8.0.0 saturation data.

  Used for: The R-410A, R-32 and R-22 rows on the refrigerant PT charts and in the superheat and subcooling calculators. The rows are stored with the site; nothing is calculated from a property engine when you use a chart.

• Chemours, Thermodynamic Properties of Opteon XL41 (R-454B).

  Used for: The R-454B chart and the R-454B option in the superheat and subcooling calculators. The source table gives psia; we convert to psig by subtracting 14.696 psi.

• NEC Table 310.16 (60°C and 75°C columns).

  Used for: Ampacities in the wire size calculator. Check the code edition your area enforces.

• NEC Chapter 9, Table 8, with K = 12.9 ohm-cmil/ft for copper and 21.2 for aluminum.

  Used for: Conductor areas in circular mils for the voltage drop calculator and the voltage drop check in the wire size calculator.

• ENERGY STAR room air conditioner sizing guideline (energystar.gov).

  Used for: Room sizes and BTU per hour in the BTU calculator, for room and window units.

• ASHRAE Fundamentals: the Huebscher equivalent-diameter relation, and the psychrometric equations in ASHRAE Handbook Fundamentals, ch. 1. Saturation vapor pressure uses the Magnus form with Alduchov-Eskridge (1996) coefficients.

  Used for: Rectangular duct sizes in the ductulator, and the psychrometric calculator.

• The Hazen-Williams equation, and pipe inside diameters from ASTM B88 (copper K/L/M), ASME B36.10 Schedule 40, and approximate PEX CTS SDR-9 values (they vary by manufacturer).

  Used for: The plumbing calculators: friction loss, pipe volume, pipe size and flow rate.

• ACCA and Farmington Consulting Group, Contractor of the Future study, as reported by ACHR News.

  Used for: The close rates by number of options presented (52% with four or more options, 42% with one to three) quoted on the homepage.

Some pages also point to ACCA Manual J and Manual D for full load and duct design. We name them so you know where to go for a full design; our calculators are not a substitute for them.

How the math is checked

• Each calculator formula is a pure function: the same inputs always give the same result, with nothing hidden.
• Each formula has unit tests that run automatically and check it against known answers.
• Tests also compare the stored refrigerant chart rows with check points at set temperatures.
• Money is worked out in whole cents, so a price never drifts by a rounding error.
• Every example number in our pricing guides comes from the site's own calculators and pricing engine, or from the BLS data file above. Example numbers are labeled as examples.
• Each calculator page shows its formula, units and a worked example, so you can check a result by hand.

Starter estimates are starting points

TierMenu loads starter tasks for each trade with estimated labor times and part costs. They are starting points, not a price list to copy. Each shop sets its own labor rate and markup, and can change every number. TierMenu never sets a shop's labor rate or markup. Check the estimates against your own costs and your own jobs before you quote with them.

How page dates work

A page's date changes only when that page's own content changes. We keep a fingerprint of each page: a short code made from its words, its tables and its search data. When we publish, the site compares each page with its fingerprint. If the content changed, the page gets a new date. If it didn't, the date stays. A change to the menu or footer that every page shares doesn't count, so we can't make a page look fresh without changing it.

What we never do

• Invent statistics or numbers.
• Invent reviews, testimonials or ratings.
• Invent customers or say how many shops use TierMenu.
• Fill a gap in code tables, refrigerant data or wage data from memory. If a number isn't in a source, it isn't on the page.

How we use AI

We use AI tools to help write and build pages. Numbers never come from an AI tool's memory. They come only from the sources listed above and from the tested formulas on this site.

Corrections

Found a mistake? Email support@tiermenu.com with the page and what looks wrong. We fix it, and the page date updates because its content changed.