Our Methodology — How Every Calculator Works
Every result on SolvWise traces to a published formula or an official standard. This page documents the math, the data sources, and how we validate accuracy.
Trust in a calculator comes from knowing what it computes. SolvWise engines use only published, peer-reviewed or regulator-recognized formulas — no proprietary 'black box' adjustments — and every page documents its formula, a worked example, and its authoritative sources.
When formulas have acknowledged limits (BMI and athletes, BMR equations at ±10%, body fat by tape measure), we state them on the page. An estimate that hides its error band is worse than an approximate one that admits its scope.
Formulas by Domain
Each calculator states its exact formula on-page. Domain standards:
- Finance: standard amortization (loan payment), annuity future value, NAV compounding — the same math CFPB consumer tools use
- Health: Mifflin-St Jeor for BMR, US Navy circumference method for body fat, WHO/CDC BMI categories, ACOG dating rules for pregnancy
- Math: IEEE-754 double precision floating point with exact integer paths for GCD/LCM (Euclidean algorithm)
- Conversion: SI-exact anchors (NIST/BIPM definitions — 1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 mi = 1609.344 m)
Precision and Rounding
Internally, calculations run at double precision (≈15-17 significant digits); display rounds only at the final step to the precision meaningful for the domain — currency to cents, body metrics to one decimal. Intermediate rounding is never applied, because chained rounding is the classic silent error.
For very large or small values the interface switches to scientific notation rather than showing misleading digit strings — a calculator that shows 0.9999999999 for 1/3×3 is exposing float artifacts, not accuracy.
Validation Process
Every calculator ships with test vectors: known-answer cases computed independently (hand-derived amortization schedules, NIST conversion tables, published BMR examples). The automated build re-runs these tests; a regression blocks deployment.
Content pages (deep dives, guides, FAQs) are reviewed against their cited sources before publication and dated with 'Last reviewed' stamps. Corrections: contact us — substantive errors are fixed within 24 hours and noted.
All Methodology Tools
Related Reading
Frequently Asked Questions
Are the calculators exact?
The math is exact to floating-point precision; the formulas themselves are estimates where their field says so (body fat from tape measurements, BMR from equations). Each page states its formula and its error band — no black boxes.
Where do the conversion constants come from?
NIST and BIPM official definitions. US customary units are defined IN metric terms by law (since the 1893 Mendenhall Order, refined 1959), so conversions like inch→cm are exact by definition, not measurement.
How are medical formulas chosen?
We use the versions current guidance recommends: Mifflin-St Jeor (Academy of Nutrition and Dietetics validation), Navy circumference method (validated vs DEXA within ±3-4%), WHO/ADA category cutoffs. Each health page cites the guideline it follows.
Do you store my inputs?
No. Calculations run in your browser; nothing you type is sent to or stored on our servers. The optional history feature is local to your browser profile.
Authoritative Sources
Last reviewed: September 2026.