Sources by type
| Source type | Citations | Share | Distinct domains |
|---|---|---|---|
| Government & regulatory agency | 48 | 22% | 21 |
| International standards body | 21 | 10% | 11 |
| Peer-reviewed research | 17 | 8% | 10 |
| Reference work or industry source | 132 | 61% | 71 |
| Total | 218 | 100% | 113 |
Counts recompute at every build from the same source list each calculator page cites, so they track the site as new tools are added.
What counts as each type
Government & regulatory agency covers federal and foreign agencies that publish the rule or table a calculator applies directly: the CDC's adult BMI cutoffs, the CFPB's mortgage amortization method under Regulation Z, the FDIC's deposit insurance limits, the Iowa DOT's asphalt density spec.
International standards body covers organizations that define the unit or format itself, not one country's application of it: BIPM for the metric system, IUPAC for chemistry nomenclature, the Unicode Consortium, ECMA International, the International Code Council, IANA's time zone database, College Board for SAT scoring.
Peer-reviewed research covers calculators built on a named, dated study: the Mifflin-St Jeor resting-energy equation (1990), the Mosteller and Du Bois body-surface-area formulas, Woods et al.'s 2015 reaction-time study, Hoeger et al.'s 2008 step-length regression.
Reference work or industry source covers everything else with a checkable citation: Wikipedia, Britannica, Wolfram MathWorld, and manufacturer or trade documents like QUIKRETE's technical data sheet or the Asphalt Institute's density range. These mostly back descriptive or historical claims: how a symbol got its shape, what a lumber grade means. None of them set a regulated number.
Home Improvement
Firewood Calculator
- Reference Connecticut Department of Consumer Protection: Firewood and Stove Wood Regulations (text of NIST Handbook 130, 2016, section 2.4)
- Reference Washington State Department of Agriculture, Weights and Measures: Firewood
- Reference Nebraska Department of Agriculture and National Conference on Weights and Measures: Avoid Getting Burned When Buying Firewood (PDF)
- Government NIST Special Publication 811, Appendix B.9: conversion factors by quantity (cord to cubic metre)
Pool Calculator
- Reference Hayward Inc., "Aqua Rite Electronic Chlorine Generator, Operation and Installation Manual" (2,700-3,400 ppm ideal salt range, 3,200 ppm optimal target, gallons-by-shape formulas including the oval 6.7 multiplier, Check Salt/High Salt warning thresholds)
- Government NIST Handbook 44, Appendix C, General Tables of Units of Measurement (exact US gallon = 231 in³, exact cubic foot = 1,728 in³, exact avoirdupois pound = 453.59237 g)
Construction
Stair Calculator
- Standards body 2021 IRC R311.7.5: stair risers, treads and dimensional limits (ICC)
- Standards body ICC: International Residential Code overview
Board Foot Calculator
- Peer-reviewed University of Wisconsin-Madison Division of Extension, Forestry, FEM-042, "What Is A Board Foot?" (the sawed-lumber board-foot formula and definition)
- Reference Wikipedia, "Board foot" (definition and formula, for general corroboration)
- Government NIST, DOC Voluntary Product Standard PS 20-20, "American Softwood Lumber Standard"
- Reference Rockler, "What Does the Quarter System of Lumber Thickness Mean?"
Asphalt Calculator
- Government Iowa Department of Transportation: Standard Specifications, Section 2303, "Hot Mix Asphalt Mixtures" (145 lb/ft³ unit weight for tonnage conversion)
- Reference Asphalt Institute: Engineering FAQs (142-148 lb/ft³ in-place density range for asphalt mixture)
- Government Federal Highway Administration: FHWA-RD-97-148, "User Guidelines for Waste and Byproduct Materials in Pavement Construction," Reclaimed Asphalt Pavement material description (100-125 lb/ft³ compacted density range)
- Reference Colorado Asphalt Pavement Association: "A Paving Fundamental: Thickness-Yield-Smoothness," compiled by James Scherocman, P.E. (loose lift vs. compacted thickness factor)
Topsoil Calculator
- Reference SDSU Extension (Hans Klopp & Anthony Bly), "Bulk Density is an Indicator of Soil Health," updated September 22, 2023 (tabulates USDA NRCS Soil Health Educators Guide 2023 ideal bulk-density ceilings by soil texture)
- Reference University of Maryland Extension, "Starting a New Lawn" (4-6 in till depth for soil amendments)
- Reference University of Maryland Extension, "Soil to Fill Raised Beds" (8 in and 12-24 in depth minimums, 20% topsoil-by-volume guidance)
Science
Engine Displacement Calculator
- Government eCFR: 40 CFR 1051.140, What is my vehicle's maximum engine power and displacement? (US EPA, recreational vehicle emission rules)
- Reference Rose-Hulman Institute of Technology, ME410 Internal Combustion Engines: Review of General Concepts (engine geometry notes, PDF)
- Reference Rose-Hulman Institute of Technology, ME410 Internal Combustion Engines: Test 1 with solutions, Fall 2002 (Honda Civic DX worked example, PDF)
- Government NIST Special Publication 811, Appendix B.8 and B.9: conversion factors (inch, cubic inch)
Molarity Calculator
- Standards body IUPAC Gold Book: amount concentration
- Government PubChem (NIH): compound molar masses
Finance
Tip Calculator
- Reference The Emily Post Institute, "Tipping Etiquette 101: A Comprehensive Guide on Tipping" (US tip percentages by service)
- Government UK Government legislation, Employment (Allocation of Tips) Act 2023 (legal requirement to pass tips to workers in full)
- Government French Ministry for the Economy (DGCCRF), "Pourboire" (service compris legally included in menu prices since 1987)
- Government Japan Travel (official Japan National Tourism Organization site), "Tipping in Japan"
- Government Fair Work Ombudsman (Australian Government), national minimum wage rates
- Reference Lonely Planet, "Tipping customs in Asia" (mainland China conventions)
- Reference Cathay Pacific, "A complete guide to tipping in the Chinese Mainland" (tour guides as the common exception)
- Government U.S. Department of Labor, Wage and Hour Division, Fact Sheet #15A: Ownership of Tips Under the FLSA
- Reference Tax Foundation, 2026 State Sales Tax Rates (range and population-weighted average)
Education
SAT Score Calculator
- Standards body College Board: Scoring Your Paper SAT Practice Test #4 (PDF, © 2023)
- Standards body College Board: SAT practice tests
Words to Pages Calculator
- Reference William Shunn, "Proper Manuscript Format": the 12-point, double-spaced formatting convention this calculator uses as its baseline
- Reference William Shunn, "The Old Rule of Thumb for Estimating Word Count Is Obsolete": why a page-based word count is an estimate, not a substitute for your word processor's exact count
- Reference Purdue OWL: MLA General Format, the 12-point font and double-spacing convention for academic papers
Health
Calorie Calculator
- Peer-reviewed Mifflin MD, St Jeor ST, et al., "A new predictive equation for resting energy expenditure in healthy individuals," American Journal of Clinical Nutrition 1990;51(2):241-247
- Peer-reviewed 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults (Circulation)
- Government NIDDK: NIH Body Weight Planner (Diabetes Discoveries & Practice Blog, Kevin D. Hall)
Steps to Miles Calculator
- Peer-reviewed Hoeger, W.W.K. et al., "One-Mile Step Count at Walking and Running Speeds," ACSM's Health & Fitness Journal, Vol. 12, No. 1, pp. 14-19 (2008), source of the 0.415 (men) / 0.413 (women) step-length-to-height regression
- Government CDC/NCHS, "Body Measurements" (FastStats), U.S. average adult height, ages 20+, NHANES 2021-2023
Body Surface Area (BSA) Calculator
- Peer-reviewed Du Bois D, Du Bois EF, "A formula to estimate the approximate surface area if height and weight be known," Archives of Internal Medicine 17(6):863-871 (1916)
- Peer-reviewed Mosteller RD, "Simplified calculation of body-surface area," New England Journal of Medicine 317(17):1098 (1987)
- Peer-reviewed Haycock GB, Schwartz GJ, Wisotsky DH, "Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults," Journal of Pediatrics 93(1):62-66 (1978)
- Peer-reviewed National Kidney Foundation, "Frequently Asked Questions About GFR Estimates" (2022), Q6 (1.73 m² indexing, Du Bois formula) and Q44 (indexed vs. non-indexed eGFR for drug dosing)
- Reference U.S. Environmental Protection Agency, Exposure Factors Handbook (2011 ed.), Chapter 7: Dermal Exposure Factors, Table 7-1 (mean total body surface area by age and sex, U.S. EPA analysis of NHANES 2005-2006 data)
Games
Click Speed Test
- Peer-reviewed Ruff, R.M. & Parker, S.B. (1993). "Gender- and age-specific changes in motor speed and eye-hand coordination in adults: normative values for the Finger Tapping and Grooved Pegboard Tests," Perceptual and Motor Skills, 76, 1219-1230
- Reference Millisecond, "Finger Tapping Test" test library (protocol description, citing Halstead, 1947, and Reitan & Wolfson, 1985)
Dice Roller & Probability Calculator
- Reference Weisstein, Eric W. "Discrete Uniform Distribution," Wolfram MathWorld
- Reference This work includes material taken from the System Reference Document 5.1 ("SRD 5.1") by Wizards of the Coast LLC and available at https://dnd.wizards.com/resources/systems-reference-document. The SRD 5.1 is licensed under the Creative Commons Attribution 4.0 International License available at https://creativecommons.org/licenses/by/4.0/legalcode. (Advantage and Disadvantage rule, p.76)
Conversion
Weight Converter
- Reference NHS Data Dictionary (May 2024), PERSON WEIGHT
- Government NIST, SI Units: Mass
- Reference National Bureau of Standards, 1959 Annual Report: International Yard and Pound
- Government NIST Handbook 44 (2026), Appendix C: troy and avoirdupois units
- Reference NIST Museum: troy pound subdivision
- Government NIST, Precious Metals Conversion Information (Handbook 130, Section 2.17)
- Government NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement
- Government legislation.gov.uk, Weights and Measures Act 1985, Schedule 1, Part VI (stone = 14 lb)
Volume Converter
- Government NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement
- Government U.S. Energy Information Administration, Glossary (Barrel)
- Reference Sizes, Inc., "English wine gallon" (1707 231 in³ standard; US 1836 adoption; UK 1824 Imperial gallon split)
- Government eCFR, 27 CFR § 5.203, Standards of Fill (Container Sizes), TTB
Electrical Converter (Watts, Amps, Volts)
- Reference Wikipedia, "Ohm's law" (voltage, current, resistance relationship)
- Reference Wikipedia, "Electric power" (P = V x I and power in AC circuits)
- Reference Wikipedia, "Power factor" (real vs. apparent power in AC circuits)
- Reference Wikipedia, "Three-phase electric power" (line-to-line vs. line-to-neutral formulas)
- Reference Wikipedia, "IEC 60038" (standard mains voltages by region)
Math
Fraction Calculator
- Standards body Common Core State Standards for Mathematics, Grade 5 Number and Operations, Fractions domain (5.NF.A.1, 5.NF.B.4)
- Standards body Common Core State Standards for Mathematics, Grade 6 The Number System (6.NS.A.1): dividing any fraction by any fraction
- Peer-reviewed Euclid, Elements, Book VII, Proposition 2: the Euclidean algorithm for the greatest common divisor
Date & Time
Date Calculator
- Government 5 U.S.C. § 6103, Thanksgiving Day fixed as the fourth Thursday in November (Cornell Legal Information Institute)
- Standards body ECMA-262, the ECMAScript Language Specification, §21.4 "Date Objects" (proleptic Gregorian calendar convention)
- Reference Microsoft Support, "DATEDIF function," Excel (the year/month/day breakdown convention this calculator follows)
World Clock & Time Zone Converter
- Standards body IANA Time Zone Database (tzdata): the authoritative source for UTC offset and daylight-saving rules this page reads live via the browser's Intl API
- Standards body ECMA-402, the ECMAScript Internationalization API Specification: defines Intl.DateTimeFormat's time-zone-aware formatting behavior
- Reference Wikipedia, "Daylight saving time in Iran" (Iran's abolition of DST, effective September 2022)
- Reference Wikipedia, "Time in India" (the 1906 adoption of UTC+5:30 as a compromise between two proposed one-hour zones)
- Reference timeanddate.com, "Time Zone & Clock Changes in Lord Howe Island" (the island's 30-minute daylight-saving shift)
Age Difference Calculator
- Reference Wikipedia, "Age disparity in sexual relationships," §"Half-your-age-plus-seven" rule
- Reference xkcd #314, "Dating Pools" (2007), origin of the "Standard Creepiness Rule" phrasing
- Reference Pew Research Center, "A growing share of U.S. husbands and wives are roughly the same age" (Aug. 2024), analysis of U.S. Census Bureau data
Food & Drink
Keg Calculator
- Government 27 CFR § 25.11, Definition of "barrel" (31 US gallons), eCFR (Electronic Code of Federal Regulations)
- Government 27 CFR § 25.156, Determination of tax on keg beer (authorized keg fractions and metric sizes), eCFR
- Government National Institute on Alcohol Abuse and Alcoholism, "What Is A Standard Drink?" (12 oz beer at ~5% ABV reference)
- Reference Siebel Institute of Technology, "How much does wasting draught beer cost a Retailer?" (draft-beer waste range)
Pizza Calculator
- Reference PMQ Pizza, "Pizza Slice Cutting Guide" (PMQ Think Tank, the pizza industry trade forum), small/medium/large slice-count convention
- Reference PMQ Pizza, "Can Cutting Pizzas into Bigger Slices Save Labor Costs?" (documented example of a chain changing its slice count)
- Reference Pizza Hut, Office & Corporate Lunch Catering (official group-ordering guidance, the "Rule of 3")
Text Tools
Sentence Counter
- Peer-reviewed Flesch, R. (1948), "A New Readability Yardstick," Journal of Applied Psychology, 32(3), 221-233 (source of the Reading Ease formula and its 206.835/1.015/84.6 constants)
- Reference Kincaid, J. P., Fishburne, R. P., Rogers, R. L., & Chissom, B. S. (1975), "Derivation of New Readability Formulas (Automated Readability Index, Fog Count and Flesch Reading Ease Formula) for Navy Enlisted Personnel," Research Branch Report 8-75, Chief of Naval Technical Training, Naval Air Station Memphis (source of the Flesch-Kincaid Grade Level formula, via Defense Technical Information Center / Internet Archive)
- Peer-reviewed Brysbaert, M. (2019), "How many words do we read per minute? A review and meta-analysis of reading rate," Journal of Memory and Language, 109
- Reference ReadabilityFormulas.com, "Learn About the Flesch Reading Ease Formula" (score-band interpretation table)
Words Per Minute (WPM) Average Calculator
- Reference Arif & Stuerzlinger (2009), "Analysis of Text Entry Performance Metrics," IEEE TIC-STH '09 (WPM formula and the 5-character-per-word convention)
- Peer-reviewed Karat, Halverson, Horn & Karat (1999), CHI '99 Proceedings, ACM (average computer user typing speeds)
- Peer-reviewed Palin, Feit, Kim, Kristensson & Oulasvirta (2019), MobileHCI '19 Proceedings, ACM (37,000-participant mobile typing study)
- Reference Wikipedia: "Words per minute" (independent cross-check of the formula, convention, and cited figures)
- Reference Guinness World Records: "Fastest realtime court reporter (stenotype writing)"
Em Dash Copy Paste
- Standards body Unicode code chart: General Punctuation (em dash U+2014)
- Standards body Unicode Character Name Index (EM DASH)
- Reference MDN: Clipboard.writeText
Real Estate
Tech
Mouse Test
- Reference Microsoft Learn: SystemInformation.DoubleClickTime Property (defines the double-click timing window the OS checks against)
- Reference Computer Hope: "How to Increase or Decrease the Mouse Double-click Speed" (default 500 ms, adjustable 200-900 ms range, Windows registry DoubleClickSpeed value)
- Reference Apple Support: "Change mouse or trackpad tracking, double-click, and scrolling speed on Mac" (macOS's relative slider, no fixed millisecond default)
- Reference MDN Web Docs: PointerEvent.getCoalescedEvents() (recovers pre-coalescing pointer samples; browser support)
- Reference Chrome Developers: "Inside look at modern web browser (part 4)" (explains why continuous input events like mousemove are coalesced to once per animation frame)
- Reference MDN Web Docs: MouseEvent.button (button-code mapping: 0=left, 1=middle, 2=right, 3=back, 4=forward)
Touchscreen Test: Find Dead Zones
- Reference MDN Web Docs: Navigator.maxTouchPoints (maximum number of simultaneous touch contact points the device supports; 0 without a touchscreen, commonly 5 on phones)
- Reference MDN Web Docs: Touch events (Touch, TouchList and TouchEvent; Touch.identifier stays consistent for the duration of each finger contact)
- Reference MDN Web Docs: TouchEvent.changedTouches (which touch points became active, moved, or were removed for each event type)
- Reference Google Android Help: "Fix a screen that isn't working right on Android" (the drag-from-corner dead-zone test, and the instruction to contact the manufacturer when it repeats in the same place)
- Reference Google Pixel Help: "Fix touch & response issues on your Pixel screen" (Touch diagnostics on Pixel 9 and later; Touch sensitivity and Screen protector mode on earlier models)
- Reference Samsung Support: "How to solve the touchscreen issue on your Samsung Galaxy device" (screen protectors and cases affecting touch, and the Touch sensitivity setting)
- Reference Samsung Support (Spanish-language page): "Que hacer si la pantalla tactil de mi Galaxy no funciona" (documents the *#0*# hardware test mode, its Touch entry, and the box-and-X drag whose uncolored areas mark a fault)
- Reference Samsung Support: "How to fix display issues on your Samsung Galaxy device" (the no-dial-code alternative: Samsung Members > Support > Phone diagnostics > Touch screen, then touch every empty area and read the result)
- Reference Apple Support: "If the screen isn't working on your iPhone or iPad" (restart, clean the glass, disconnect accessories, remove cases and screen protectors before service)
Refresh Rate Test: Check Your Screen's Real Hz
- Reference MDN Web Docs: Window.requestAnimationFrame() (callback runs "before the next repaint"; its frequency "will generally match the display refresh rate"; 60Hz named as the most common rate with 75, 120 and 144 widely used; calls are paused in background tabs and hidden iframes)
- Reference MDN Web Docs: Performance.now() (returns a DOMHighResTimeStamp in milliseconds, "not limited to one-millisecond resolution", unlike Date.now())
- Reference MDN Web Docs: Document.visibilityState (the "visible" and "hidden" states this page checks before and during a measurement)
- Reference Wikipedia: "Refresh rate" (defines refresh rate as the number of times per second a raster display shows a new image, notes it "can be independent of frame rate", and records the frame persistence figures of about 16.7 ms at 60 Hz and 6.9 ms at 144 Hz; checked 2026-10-16)
Scroll Test: Check Wheel Skips, Direction & Speed
- Reference MDN Web Docs: WheelEvent (deltaX / deltaY / deltaZ and the event fired when the user rotates a wheel device)
- Reference MDN Web Docs: WheelEvent.deltaMode (0 = pixels, 1 = lines, 2 = pages)
- Reference MDN Web Docs: WheelEvent.deltaY (vertical scroll amount in units of deltaMode)
- Reference Pointer Events Level 4 W3C specification: WheelEvent interface (normative deltaMode and DOM_DELTA_PIXEL / LINE / PAGE; Wheel Events moved here from UI Events)
Sound Test: Left / Right Speaker Check in the Browser
- Reference MDN Web Docs: StereoPannerNode (pan from -1 left to +1 right)
- Reference MDN Web Docs: OscillatorNode (sine / square / sawtooth / triangle tones)
- Reference MDN Web Docs: AudioContext (audio graph destination for speakers and headphones)
- Reference MDN Web Docs: GainNode (volume stage used before the panner on this page)
- Reference Web Audio API W3C recommendation: StereoPannerNode section (normative pan model)
MP3 Converter
- Reference MDN Web Docs: BaseAudioContext.decodeAudioData (decode a complete audio file to PCM)
- Reference MDN Web Docs: OfflineAudioContext (render PCM at a chosen sample rate, including resampling)
- Standards body ISO/IEC 11172-3:1993, MPEG-1 Audio (Layer III; 32, 44.1, and 48 kHz)
- Reference Wikipedia: MP3 (MPEG-1 Layer III bitrate list, 32 through 320 kbps, and the 320 kbps frame-size note)
- Reference LAME project: About LAME (LGPL MPEG Layer III encoder, CBR and VBR)
- Reference lamejs (the ES-module port this page runs, @breezystack/lamejs)
- Reference Web Audio API W3C recommendation: Down Mixing Speaker Layouts (quad and 5.1 to stereo)
Sports
Golf Club Distance Chart
- Reference TrackMan, "What is Club Speed?" (average amateur and Tour clubhead speed/distance data)
- Reference Golf.com, "This is how far PGA and LPGA Tour players hit it with every club"
- Reference PlayBetter, "Golf Club Distance Charts for Men and Women" (skill-level distance chart)
- Reference MyGolfSpy, "Golf Club Gapping Tool" (healthy gap-range guidance)