Sources & editorial standards
CalcWisp cites 103 primary sources from 34 publishers. This page lists every one, with the pages that rely on it, so you can check any number on the site against the original. Read about us for who builds the site.
Our standards
- Authoritative sources for money, tax, health and measurement figures: government agencies, standards bodies, universities and peer-reviewed research, plus official documentation from the maker where a guide covers a product. Never another calculator site.
- Every worked example is recalculated in code, and the calculators are covered by automated tests that compare their results with these sources. A change that breaks a test does not go live.
- Year-specific figures are dated (for example, 2026 tax brackets) and reviewed when new numbers are published.
- Corrections: email hello@calcwisp.com with the page and the figure; we check it against the source and fix it.
Internal Revenue Service (IRS)
- IRS — Topic no. 751, Social Security and Medicare withholding rates — used in Social Security Tax Rate 2026: 6.2%, the $184,500 Wage Base, Medicare and Self-Employment
- IRS — Topic no. 560, Additional Medicare Tax — used in Social Security Tax Rate 2026: 6.2%, the $184,500 Wage Base, Medicare and Self-Employment, Paycheck calculator
- IRS — Self-employment tax (Social Security and Medicare taxes) — used in Social Security Tax Rate 2026: 6.2%, the $184,500 Wage Base, Medicare and Self-Employment
- IRS — 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500 — used in 401(k) Contribution Limits 2026: Employee, Catch-Up, Ages 60–63 and Total Limit, Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs, Roth IRA Income Limits 2026: Phase-Out Ranges, Contribution Limits and Examples
- IRS — Retirement topics: 401(k) and profit-sharing plan contribution limits — used in 401(k) Contribution Limits 2026: Employee, Catch-Up, Ages 60–63 and Total Limit
- IRS — Retirement topics: Catch-up contributions — used in 401(k) Contribution Limits 2026: Employee, Catch-Up, Ages 60–63 and Total Limit
- IRS — Cost-of-Living Adjustments for Retirement Items, 1989–2025 (COLA table) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2024-80 (2025 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2023-75 (2024 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2022-55 (2023 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2021-61 (2022 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2020-79 (2021 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2019-59 (2020 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2018-83 (2019 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2017-64 (2018 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2016-62 (2017 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Notice 2015-75 (2016 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — IR-2014-99 (2015 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — IR-2013-86 (2014 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — IR-2012-77 (2013 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — IR-2010-108 (2011 amounts) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (2010), What's New for 2010 and 2011 — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (2009) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (2008), What's New for 2008 and 2009 — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — IR-2007-171 (2008 amounts, 2007 comparison) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (2006), What's New for 2007 — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — AT-2001-54, Roth IRAs (2001 limits) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — T.D. 8816, final Roth IRA regulations (§1.408A-3), effective for tax years from 1998 — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (1998) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (1999) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590 (2000) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs
- IRS — Publication 590-A, Contributions to Individual Retirement Arrangements (deadline, reduced-limit worksheet) — used in Roth IRA Contribution Limits by Year (1998–2026), With Income Phase-Outs, Roth IRA Income Limits 2026: Phase-Out Ranges, Contribution Limits and Examples
- IRS — Notice 2025-67, 2026 Amounts Relating to Retirement Plans and IRAs — used in Roth IRA Income Limits 2026: Phase-Out Ranges, Contribution Limits and Examples
- IRS — Amount of Roth IRA contributions that you can make for 2024 (reduction method) — used in Roth IRA Income Limits 2026: Phase-Out Ranges, Contribution Limits and Examples
- IRS — Retirement topics: IRA contribution limits — used in Roth IRA Income Limits 2026: Phase-Out Ranges, Contribution Limits and Examples
- IRS — Retirement plans FAQs regarding required minimum distributions — used in RMD Table 2026: IRS Uniform Lifetime Table and How to Calculate Your RMD
- IRS — Retirement topics: Required minimum distributions (RMDs) — used in RMD Table 2026: IRS Uniform Lifetime Table and How to Calculate Your RMD
- IRS — Publication 590-B, Distributions from Individual Retirement Arrangements — used in RMD Table 2026: IRS Uniform Lifetime Table and How to Calculate Your RMD
- IRS — IRA required minimum distribution worksheet — used in RMD Table 2026: IRS Uniform Lifetime Table and How to Calculate Your RMD
- IRS — Internal Revenue Bulletin 2024-33 (proposed RMD regulations under SECURE 2.0) — used in RMD Table 2026: IRS Uniform Lifetime Table and How to Calculate Your RMD
- IRS — Topic no. 403, Interest received — used in CD vs High-Yield Savings: Which Earns More and When Each Makes Sense
- IRS Revenue Procedure 2025-32 (2026 tax brackets) — used in Paycheck calculator
- https://www.irs.gov/newsroom/irs-releases-tax-inflation-adjustments-for-tax-year-2026-including-amendments-from-the-one-big-beautiful-bill — used in Paycheck calculator
National Institute of Standards and Technology (NIST)
- NIST Guide to the SI (SP 811), Appendix B.8 — Factors for Units Listed Alphabetically — used in Time Conversions: Seconds, Hours and Weeks in a Year, Weight Conversions: Grams, Ounces, Pounds, Kilograms, Length and Distance: Inches, Feet, Miles, km and Acres and 6 more
- NIST — SI Units: Time — used in Time Conversions: Seconds, Hours and Weeks in a Year
- NIST — SI Units — used in Weight Conversions: Grams, Ounces, Pounds, Kilograms, Metric vs Imperial: Differences, Units and Conversions, How to Read a Tape Measure (Inches, Fractions, Metric)
- NIST — Metric (SI) Prefixes — used in Weight Conversions: Grams, Ounces, Pounds, Kilograms, Length and Distance: Inches, Feet, Miles, km and Acres, Liquid Volume: Pints, Quarts, Gallons and Liters Chart
- NIST — The US Survey Foot and the International Foot — used in Length and Distance: Inches, Feet, Miles, km and Acres
- NIST — U.S. Survey Foot: Revised Unit Conversion Factors — used in Length and Distance: Inches, Feet, Miles, km and Acres
- NIST Handbook 44, Appendix C — General Tables of Units of Measurement (2026) — used in Length and Distance: Inches, Feet, Miles, km and Acres
- NIST — Equivalents of the Common Capacity Units (table) — used in US Kitchen Measurements: Cups, Tablespoons, Teaspoons, mL
- NIST Office of Weights and Measures — Metric Kitchen: Culinary Measurement Tips — used in US Kitchen Measurements: Cups, Tablespoons, Teaspoons, mL
- NIST/SEMATECH e-Handbook of Statistical Methods — 1.3.5.6 Measures of Scale — used in How to Find Standard Deviation (Sample and Population, Step by Step)
- NIST Office of Weights and Measures — SI Units: Temperature — used in How to Convert Celsius to Fahrenheit (Formula, Shortcut and Chart)
Consumer Financial Protection Bureau (CFPB)
- CFPB — What is a debt-to-income ratio? — used in What Is a Good Debt-to-Income Ratio? Thresholds, Examples and How to Lower It
- CFPB — Qualified Mortgage Definition: General QM Loan Definition final rule — used in What Is a Good Debt-to-Income Ratio? Thresholds, Examples and How to Lower It
- CFPB — General QM Loan Definition: Delay of Mandatory Compliance Date — used in What Is a Good Debt-to-Income Ratio? Thresholds, Examples and How to Lower It
- CFPB — What is a certificate of deposit (CD)? — used in CD vs High-Yield Savings: Which Earns More and When Each Makes Sense
- CFPB — Regulation DD (Truth in Savings) §1030.2 Definitions — used in CD vs High-Yield Savings: Which Earns More and When Each Makes Sense
- CFPB — Regulation DD (Truth in Savings) §1030.4 Account disclosures — used in CD vs High-Yield Savings: Which Earns More and When Each Makes Sense
OpenStax (Rice University)
- OpenStax Prealgebra 2e — 5.1 Decimals — used in How to Convert a Decimal to a Fraction (Terminating and Repeating, With Chart)
- OpenStax Contemporary Mathematics — 3.4 Rational Numbers — used in How to Convert a Decimal to a Fraction (Terminating and Repeating, With Chart)
- OpenStax Prealgebra 2e — 6.1 Understand Percent — used in How to Calculate a Percentage (Percent of a Number, Percent Change, Reverse Percent)
- OpenStax Prealgebra 2e — 6.2 Solve General Applications of Percent — used in How to Calculate a Percentage (Percent of a Number, Percent Change, Reverse Percent)
- OpenStax Prealgebra 2e — 6.5 Solve Proportions and their Applications — used in How to Calculate a Percentage (Percent of a Number, Percent Change, Reverse Percent)
National Institutes of Health (NIH / PubMed)
- Mifflin MD et al. — A new predictive equation for resting energy expenditure in healthy individuals (Am J Clin Nutr, 1990; PubMed) — used in How to Calculate Macros (Step-by-Step With a Worked Example)
- National Academies via NCBI Bookshelf — Current Applications of the Acceptable Macronutrient Distribution Range — used in How to Calculate Macros (Step-by-Step With a Worked Example)
- NCBI PMC — Come Back Skinfolds, All Is Forgiven: A Narrative Review of the Efficacy of Common Body Composition Methods in Applied Sports Practice — used in How to Calculate Body Fat Percentage (Navy Method and Other Ways)
acefitness.org
Defense Technical Information Center (DTIC)
- Hodgdon JA, Beckett MB — Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height (NHRC Report 84-11, 1984; DTIC) — used in How to Calculate Body Fat Percentage (Navy Method and Other Ways)
- Hodgdon JA, Beckett MB — Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height (NHRC Report 84-29, 1984; DTIC) — used in How to Calculate Body Fat Percentage (Navy Method and Other Ways)
support.apple.com
support.microsoft.com
USDA Food Safety and Inspection Service
- USDA FSIS — Let's Talk Turkey: A Consumer Guide to Safely Roasting a Turkey — used in How Much Turkey Per Person: 1 Pound Each, 1.5 With Leftovers (Chart), How Long to Thaw a Turkey: Fridge and Cold-Water Times by Weight (USDA)
- USDA FSIS — Safe Defrosting — used in How Long to Thaw a Turkey: Fridge and Cold-Water Times by Weight (USDA)