Every FigureNerd calculator goes through extensive industry-specific investigative research. We name our sources, document our formulas, and have them reviewed by domain experts. No black-box math.
FigureNerd calculators start with a question a real person is trying to answer: "How much HVAC do I need for a Minnesota winter?" or "Does switching to an S-corp actually save me money?" We do not start with a formula from a textbook and work outward. We start with the real-world problem and work backward to find the right formula.
Every calculator follows a four-layer methodology. It is the same process whether we are building an HVAC load sizing tool or a retirement runway stress-test. The layers are not optional. A calculator cannot ship until all four are complete.
We read the top three competitor tools for each topic. We document what they get right and where they fall short, including regional adjustments they miss, edge cases they ignore, and explanations that assume too much. Calculator.net is always one of the three because they are the volume leader in the calculator space.
We identify the authoritative data source for each topic: ACCA Manual J for HVAC sizing, IRS publications for tax, NEEP for heat pump performance, Fannie Mae guidelines for mortgage, RSMeans for construction. We read the source documents, not the summaries.
The calculator and its documentation file are built at the same time, not after. Every formula gets a co-located documentation file with eight required sections: experts referenced, reference tools benchmarked, formula derivation, regional factors, test cases, disclaimer, sources, and update log.
Domain-sensitive values are reviewed by the relevant partner before any calculator goes live. HVAC tonnage tables and mechanical systems values get reviewed by the partner with 30+ years in HVAC-R and refrigeration. Tax and financial math gets reviewed by the partner with 40+ years in small-business operations, real estate, and personal finance.
Every calculator names its primary source on the tool page. We link to the actual document, not just the agency homepage. Here is the full list of primary sources by topic:
FigureNerd is built by two founding partners with 70+ combined years of direct field experience. One partner brings 40+ years in CEO operations, small-business management, real estate, asset protection, portfolio building, and personal finance. The other is an HVAC, refrigeration, and mechanical industry legend whose reputation precedes him. He brings 30+ years in HVAC-R, mechanical systems, construction, and trades.
Domain review means one of them has looked at the core formula values and said they reflect real-world results, not just textbook math. The founding example of why this matters: a Simplified Manual J formula applied without regional adjustment recommended 5 tons of cooling for 2,000 sq ft in Fargo, North Dakota. That is the number for Miami. The partner with 30+ years in the field caught it. Fargo at 2,000 sq ft is closer to 2.5 to 3 tons depending on insulation and climate zone. The corrected value is now SCOTT-VERIFIED and locked in the calculator's documentation.
That correction is why the review step is not optional. Textbook formulas applied without regional context produce wrong answers. Our domain experts have installed systems and filed returns and managed properties in real climates with real clients. That is what the verification step captures.
Every FigureNerd calculator page displays a "Last reviewed" date. When tax rates change (IRS updates brackets and limits each year in October and November), we update the affected calculators before January 1. When EPA regulations change refrigerant rules, we update the HVAC calculators. When FHFA publishes new conforming loan limits, we update the mortgage tools.
The update process follows the same four-layer methodology as the initial build. We do not just change a number. We verify the new rate against the primary source, update the formula documentation, and confirm the change does not break any of the locked test cases.
The "Last reviewed" stamp on each calculator reflects when someone on the team actually reviewed the formula against current primary sources, not just when the page was last edited.
Each topic cluster has its own primary authority and formula approach. Here is how we build within each cluster:
Load sizing follows ACCA Manual J with IECC climate zone multipliers. Heat pump performance uses NEEP ccASHP published category averages at 47F, 17F, 0F, and -13F. Refrigerant comparison uses EPA AIM Act GWP figures and phase-down timeline.
Expert review: 30+ years HVAC-R field experience, including cold-climate installs in Zones 5 through 7.
Source: ACCA Manual J, 8th Ed.Self-employment tax uses the 92.35% net earnings multiplier from IRS Publication 334. Quarterly estimates use the safe harbor rules from IRS Publication 505. S-corp reasonable compensation benchmarks come from BLS Occupational Employment Statistics.
Expert review: 40+ years small-business operations, entity structure, and tax planning.
Source: IRS Pub 334, 505, 5351031 exchange failure cost uses the depreciation recapture rate (25%), LTCG rates, and NIIT (3.8%) from IRC sections 1245, 1250, 1411, and 1031. Fannie Mae and FHFA set the conforming loan limits used in mortgage tools.
Expert review: 40+ years real estate investment, asset protection, and portfolio management.
Source: IRC 1031, IRS Pub 544Heat pump payback uses DOE climate zone COP adjustments, ENERGY STAR product specifications, and current IRS 25C credit limits. EV charging cost uses EIA state electricity price data and manufacturer-published charge efficiency ratings.
Expert review: HVAC-R partner reviews mechanical specifications; finance partner reviews credit calculations.
Source: DOE, ENERGY STAR, IRS 25CDrywall quantity uses the RSMeans industry-standard formula (square footage plus waste factor plus door and window deductions). Construction sequence follows field-validated phase ordering from the partner with 30+ years in construction and mechanical trades.
Expert review: 30+ years construction and trades field experience.
Source: RSMeans Cost DataRetirement runway uses Social Security Administration benefit rules, state-by-state Social Security taxability rules (approximately 9 to 10 states tax SS benefits as of 2026), and sequence-of-returns modeling. Longevity scenarios run to age 100.
Expert review: 40+ years personal finance and portfolio management.
Source: SSA, IRS Pub 915All primary sources used across FigureNerd calculators, with direct links to the authoritative documents:
Have a question about a specific calculator's methodology? The documentation file for each calculator is available by request. Contact us via the feedback link on any calculator page.