Methodology: how we calculate and review

Every SizeBench calculator answers one practical question and shows the full math. This page explains where the formulas come from, how we check the results and how we keep the content current.

1. Sources and standards

We work from published technical standards and official sources. Where the rules differ by country, each language version follows the local code, for example the NEC in the United States, NBR 5410 in Brazil and DIN VDE in Germany.

Electrical

• NFPA 70 – National Electrical Code (NEC)
• IEC 60364-5-52

Solar & Battery

• NREL PVWatts

HVAC & Air Conditioning

• ASHRAE Handbook – Fundamentals

Electronics

• IEC 60062 – marking codes for resistors and capacitors
• IEC 60063 – preferred number series (E12, E24)

Networking & Telecom

• IEEE 802.3 (Ethernet, PoE)
• RFC 4632 / RFC 1918 (IPv4)

Marine & RV

• ABYC E-11 – AC & DC Electrical Systems on Boats

Construction & Home

• ACI – American Concrete Institute

EV Charging

• IEC 61851-1 – EV conductive charging
• SAE J1772

3D Printing

• Filament manufacturer datasheets (density, diameter)

Unit Converters

• NIST SP 811 – Guide for the Use of the SI
• BIPM – The SI Brochure

2. How we calculate

• Reference formulas: current, voltage drop, power, energy and unit conversions use the standard engineering equations found in textbooks and codes.
• Code tables: conductor ampacity, standard wire sizes and standard breaker ratings come from the published tables. When a result falls between two sizes we always pick the next larger standard size (the safe side).
• Visible assumptions: ambient temperature, insulation type, installation method and efficiency are shown as fields or stated in the text, and you can change them.
• Exact factors: unit conversions use the factors from NIST SP 811 and the SI Brochure (BIPM).

3. How we verify

• The math runs in your browser with the same code for every language, so there is never a second version of a formula.
• Before every release an automated test opens every quick-answer page in a real browser and checks that the number shown is exactly what the calculator returns for the same inputs. If it does not match, the page is not published.
• We check results against worked examples in the standards and against manufacturers' published tables.

4. Review dates

Each page shows “Reviewed on” with the date its content was last checked. The date changes only when the content actually changes; we never refresh dates without a review.

5. Use of automation and AI

We use automation and AI tools to help draft and translate explanatory text. Numbers are never typed by hand or generated by AI: they all come from the calculators' code and pass the tests above. The team defines the formulas, standards and assumptions and reviews what is published.

6. Corrections

Found an error or an outdated code reference? Email hello@sizebench.com. We fix it, re-test it, and the page's review date shows the correction.

7. Limits

Results are estimates for planning and learning. Electrical work must follow the code in force where you live and be done by a qualified electrician. See our disclaimer.