Bureau of Concurrent Hygiene · Est. 1954
Bureau of Concurrent Hygiene
Technical annex · Form 35/09

Methodology and sources

The Bureau publishes its methods in full.

Method

  1. Each shower can absorb one brushing and one urination.
  2. The time saved per absorbing shower is the brushing time, the urination time, and the post-urination procedures, less any extension if the tasks exceed the shower's length.
  3. Brushings and urinations beyond the number of showers are not absorbed.
  4. Forfeiture to date accrues from the age of accountability. Forfeiture ahead accrues until the expected lifespan from the U.S. life table.
  5. National figures apply population defaults to the eligible, non-compliant population.

Limitations

  • Assumes current habits have held since the age of accountability.
  • Assumes at least one free hand.
  • Assumes each shower can absorb one brushing and one urination.
  • National figures use population defaults, not your inputs.
  • Yang et al. measured full bladders across species. The Bureau's application to consolidation is an extrapolation.
Table M1. Constants and sources
IDConstantValueStatusSource
R1Duration of urination (the Law of Urination)21 sSourcedhttps://doi.org/10.1073/pnas.1402289111
R2Recommended toothbrushing duration120 sSourcedhttps://www.ada.org/resources/ada-library/oral-health-topics/toothbrushes
R3Average U.S. shower duration7.8 minSourcedhttps://www.awwa.org/wp-content/uploads/Water-Conservation-Residential-End-Uses-of-Water.pdf
R4Average actual toothbrushing duration87 sSourcedhttps://doi.org/10.1111/idh.70048
R5Recommended handwashing scrub time20 sSourcedhttps://www.cdc.gov/clean-hands/about/index.html
R6Post-urination procedures (flushing, handwashing, drying)40 sBureau estimateBureau estimate: flushing and lid management (5 s), wetting and lathering (5 s), scrubbing for the CDC minimum of 20 s (see R5), and rinsing and drying (10 s).
R7Typical urinations per day7 per daySourcedhttps://doi.org/10.1097/01.ju.0000135890.08541.02
R7LLower bound of normal urination frequency4 per daySourcedhttps://health.clevelandclinic.org/how-often-should-you-pee
R8Remaining life expectancy by age (United States, total population)—Sourcedhttps://www.cdc.gov/nchs/data/nvsr/nvsr75/nvsr75-05.pdf
R9Standard U.S. bathroom wall tile, side length (4¼ inches)0.10795 mSourcedhttps://digitalassets.daltile.com/content/dam/Daltile/website/resources/products/pattern-guides/DAL_ColorWheel-Classic_TilePatternGuide.pdf
R10U.S. resident population341,784,857 peopleSourcedhttps://www.census.gov/data/tables/time-series/demo/popest/2020s-national-total.html
R11Share of U.S. population aged 6 and older0.9346815122356342 shareSourcedhttps://www.census.gov/data/tables/time-series/demo/popest/2020s-national-detail.html
R12Showers per person per day (United States)0.7025316455696202 per daySourcedhttps://www.awwa.org/wp-content/uploads/Water-Conservation-Residential-End-Uses-of-Water.pdf
R13Share of residents who brush their teeth outside the shower0.9 shareBureau estimateBureau estimate: industry polls find that about 4% of Americans brush most often in the shower (Delta Dental, 2014) and 23% brush there at least sometimes (Moen, 2023), so the Bureau assumes 90% of residents brush their teeth outside it.
R14Share of residents who urinate outside the shower0.8 shareBureau estimateBureau estimate: polls put habitual shower urination at about 13% of adults (YouGov, 2014: 62% had ever done it, and 21% of those do it every or most times) to 24% (Talker Research, 2025: 12% daily and 12% a few times a week), so the Bureau assumes 80% of residents urinate outside the shower.
R15Empire State Building construction labor7,000,000 hoursSourcedhttps://www.esbnyc.com/sites/default/files/esb_fact_sheet_final.pdf
R16Hours per doctorate11,856 hoursSourcedhttps://ncses.nsf.gov/pubs/nsf25349/assets/nsf25349.pdf
R17U.S. research doctorates awarded per year58,131 per yearSourcedhttps://ncses.nsf.gov/pubs/nsf26315/report
R18Toilet flush volume (U.S. federal maximum, 1.6 gallons)6.0566588544 LSourcedhttps://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-C/section-430.32
R19Olympic swimming pool volume3,125,000 LSourcedhttps://resources.fina.org/fina/document/2026/02/18/e6815ecc-06d9-4f0b-98e9-4c441cf5e6a3/2026-02-18_World-Aquatics_CR-Final.pdf
R20Shower flow rate (U.S. federal maximum, 2.5 gallons per minute)9.46352946 L/minSourcedhttps://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-C/section-430.32
R22Pelvic-floor caution on habitual shower urination—Sourcedhttps://health.clevelandclinic.org/is-it-ok-to-pee-in-the-shower
R23Toothbrush storage guidance—Sourcedhttps://www.mouthhealthy.org/all-topics-a-z/toothbrushes
R24Shower transaction overhead (undressing, drying, dressing)240 sBureau estimateBureau estimate: undressing (60 s), towelling dry (90 s) and dressing (90 s) around a shower that exists only to absorb one task.
R25Dermatological guidance on shower frequency—Sourcedhttps://www.health.harvard.edu/blog/showering-daily-is-it-necessary-2019062617193
R26Guidance against restricting fluids or delaying urination—Sourcedhttps://www.niddk.nih.gov/health-information/urologic-diseases/bladder-control-problems/prevention
R27U.S. GDP per hour worked97.05 USD/hSourcedhttps://doi.org/10.1787/b024d9e1-en
Table M2. Comparison durations
IDUndertakingHoursStatusSource
apollo-11Apollo 11 mission duration195.31Sourcedhttps://www.nasa.gov/history/apollo-11-mission-overview/
ring-cycleWagner, Der Ring des Nibelungen, total performance time15.00Sourcedhttps://www.rbo.org.uk/opera-essentials-ring-cycle
marathonAverage marathon finishing time4.57Sourcedhttps://runrepeat.com/the-state-of-us-marathons-2025
channel-swimAverage solo English Channel swim13.59Sourcedhttps://cspf.co.uk/solo-swims-statistics-2
pilot-licensePrivate pilot license, minimum flight time40.00Sourcedhttps://www.ecfr.gov/current/title-14/chapter-I/subchapter-D/part-61/subpart-E/section-61.109
spanishSpanish to professional working proficiency690.00Sourcedhttps://www.state.gov/national-foreign-affairs-training-center/foreign-language-training
war-and-peaceReading War and Peace36.06Sourcedhttps://doi.org/10.1016/j.jml.2019.104047
friendsFriends (1994–2004), all 236 episodes, total running time90.00Sourcedhttps://bluray.highdefdigest.com/7254/friends_complete.html
beatles-catalogueThe Beatles’ core catalogue, total running time10.29Sourcedhttps://en.wikipedia.org/wiki/The_Beatles_discography
longest-flightWorld’s longest scheduled flight (New York JFK–Singapore)19.25Sourcedhttps://www.thenationalnews.com/travel/2026/07/13/longest-flights-singapore-qantas-emirates/
coast-to-coastDriving time, New York City to Los Angeles41.00Sourcedhttps://www.upack.com/articles/what-is-the-best-driving-route-from-california-to-new-york
ironmanAverage IRONMAN (140.6-mile) finishing time12.81Sourcedhttps://doi.org/10.1371/journal.pone.0311202
work-weekStandard workweek40.00Sourcedhttps://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title29-section207&num=0&edition=prelim

Notes

  1. American Dental Association. Oral Health Topics: Toothbrushes (last updated August 2026): the ADA recommends brushing teeth twice a day for two minutes using a fluoride toothpaste. https://www.ada.org/resources/ada-library/oral-health-topics/toothbrushes Accessed 2026-09-25.
  2. Thomassen, T. M. J. A., Hu, Y. S. R., van der Weijden, F. A., & Slot, D. E. (2026). Exploring toothbrushing duration among adults: A systematic review. International Journal of Dental Hygiene. https://doi.org/10.1111/idh.70048 Accessed 2026-09-25.
  3. DeOreo, W. B., Mayer, P., Dziegielewski, B., & Kiefer, J. (2016). Residential End Uses of Water, Version 2: Executive Report. Water Research Foundation, p. 9: “The average duration held steady at 7.8 minutes per shower.” https://www.awwa.org/wp-content/uploads/Water-Conservation-Residential-End-Uses-of-Water.pdf Accessed 2026-09-25.
  4. Yang, P. J., Pham, J., Choo, J., & Hu, D. L. (2014). Duration of urination does not change with body size. Proceedings of the National Academy of Sciences, 111(33), 11932–11937. https://doi.org/10.1073/pnas.1402289111 Accessed 2026-09-25.
  5. Centers for Disease Control and Prevention. About Handwashing (Clean Hands): “Scrub your hands for at least 20 seconds.” https://www.cdc.gov/clean-hands/about/index.html Accessed 2026-09-25.
  6. Bureau estimate: flushing and lid management (5 s), wetting and lathering (5 s), scrubbing for the CDC minimum of 20 s (see R5), and rinsing and drying (10 s).
  7. Latini, J. M., Mueller, E., Lux, M. M., Fitzgerald, M. P., & Kreder, K. J. (2004). Voiding frequency in a sample of asymptomatic American men. Journal of Urology, 172(3), 980–984 (median 7 voids per 24 h); and Fitzgerald, M. P., & Brubaker, L. (2003). Variability of 24-hour voiding diary variables among asymptomatic women. Journal of Urology, 169(1), 207–209 (median 8, then 7). https://doi.org/10.1097/01.ju.0000135890.08541.02 Accessed 2026-09-25.
  8. Cleveland Clinic Health Essentials (18 October 2024). How Often Should You Pee During the Day? Urologist Raevti Bole, MD: some people “may go only four times over a 24-hour timeframe, and that’s also usually fine.” https://health.clevelandclinic.org/how-often-should-you-pee Accessed 2026-09-25.
  9. Arias, E., Xu, J. Q., & Tejada-Vera, B. (2026). United States life tables, 2024. National Vital Statistics Reports, 75(5). National Center for Health Statistics. Table 1 (total population), column eₓ. https://www.cdc.gov/nchs/data/nvsr/nvsr75/nvsr75-05.pdf Accessed 2026-09-25.
  10. Daltile. Color Wheel Classic wall tile pattern guide: the nominal “4x4” glazed ceramic wall tile measures 4-1/4" x 4-1/4". https://digitalassets.daltile.com/content/dam/Daltile/website/resources/products/pattern-guides/DAL_ColorWheel-Classic_TilePatternGuide.pdf Accessed 2026-09-25.
  11. U.S. Census Bureau, Population Division. Annual Estimates of the Resident Population for the United States, Regions, States, District of Columbia, and Puerto Rico: April 1, 2020 to July 1, 2025 (NST-EST2025-POP), Vintage 2025: resident population on July 1, 2025. https://www.census.gov/data/tables/time-series/demo/popest/2020s-national-total.html Accessed 2026-09-25.
  12. U.S. Census Bureau, Population Division. Annual Estimates of the Resident Population by Single Year of Age and Sex for the United States: April 1, 2020 to July 1, 2025 (NC-EST2025-SYASEXN), Vintage 2025. https://www.census.gov/data/tables/time-series/demo/popest/2020s-national-detail.html Accessed 2026-09-25.
  13. Derived from DeOreo, W. B., et al. (2016). Residential End Uses of Water, Version 2. Water Research Foundation: shower use of 11.1 gallons per person per day (Executive Report, Fig. 5) divided by 15.8 gallons per average shower. https://www.awwa.org/wp-content/uploads/Water-Conservation-Residential-End-Uses-of-Water.pdf Accessed 2026-09-25.
  14. Bureau estimate: industry polls find that about 4% of Americans brush most often in the shower (Delta Dental, 2014) and 23% brush there at least sometimes (Moen, 2023), so the Bureau assumes 90% of residents brush their teeth outside it.
  15. Bureau estimate: polls put habitual shower urination at about 13% of adults (YouGov, 2014: 62% had ever done it, and 21% of those do it every or most times) to 24% (Talker Research, 2025: 12% daily and 12% a few times a week), so the Bureau assumes 80% of residents urinate outside the shower.
  16. Empire State Building. Official fact sheet: “More than 7 million man hours were logged in the Empire State Building’s construction.” https://www.esbnyc.com/sites/default/files/esb_fact_sheet_final.pdf Accessed 2026-09-25.
  17. Derived: National Center for Science and Engineering Statistics (2025). Doctorate Recipients from U.S. Universities: 2024 Data Tables (NSF 25-349), Table 1-12: median 5.7 years from starting the doctoral program to the doctorate, all fields, 2024; multiplied by 2,080 full-time hours per year. https://ncses.nsf.gov/pubs/nsf25349/assets/nsf25349.pdf Accessed 2026-09-25.
  18. National Center for Science and Engineering Statistics (2026). Doctorate Recipients from U.S. Universities: 2024 (NSF 26-315): research doctoral degrees awarded by U.S. institutions rose from 57,806 in 2023 to 58,131 in 2024. https://ncses.nsf.gov/pubs/nsf26315/report Accessed 2026-09-25.
  19. 10 CFR § 430.32(q): maximum 1.6 gallons per flush for gravity tank, flushometer tank and electromechanical hydraulic water closets manufactured after January 1, 1994. https://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-C/section-430.32 Accessed 2026-09-25.
  20. World Aquatics. Competition Regulations (in force from February 2026), Part Two, rules 15.1.1, 15.3.1 and 15.4.1: 50 m pools with a minimum width of 25 m and a minimum depth of 2.5 m at the Olympic Games and World Aquatics Championships. https://resources.fina.org/fina/document/2026/02/18/e6815ecc-06d9-4f0b-98e9-4c441cf5e6a3/2026-02-18_World-Aquatics_CR-Final.pdf Accessed 2026-09-25.
  21. 10 CFR § 430.32(p): maximum 2.5 gallons per minute for showerheads manufactured after January 1, 1994, measured at a flowing pressure of 80 pounds per square inch gage. https://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-C/section-430.32 Accessed 2026-09-25.
  22. Bureau estimate: undressing (60 s), towelling dry (90 s) and dressing (90 s) around a shower that exists only to absorb one task.
  23. Cleveland Clinic Health Essentials (24 June 2025). It’s Generally OK To Pee in the Shower — With a Few Exceptions. Urologist Neel Parekh, MD. https://health.clevelandclinic.org/is-it-ok-to-pee-in-the-shower Accessed 2026-09-25.
  24. American Dental Association. MouthHealthy: Toothbrushes (toothbrush care). https://www.mouthhealthy.org/all-topics-a-z/toothbrushes Accessed 2026-09-25.
  25. Shmerling, R. H. (updated 16 August 2021). Showering daily — is it necessary? Harvard Health Publishing. https://www.health.harvard.edu/blog/showering-daily-is-it-necessary-2019062617193 Accessed 2026-09-25.
  26. National Institute of Diabetes and Digestive and Kidney Diseases. Prevention of Bladder Control Problems (Urinary Incontinence) & Bladder Health (last reviewed July 2021). https://www.niddk.nih.gov/health-information/urologic-diseases/bladder-control-problems/prevention Accessed 2026-09-25.
  27. OECD (2025). OECD Compendium of Productivity Indicators 2025, Figure 4.6, “Labour productivity in 2023: GDP per hour worked in current prices and current PPPs”: United States, USD 27,720,709 million of GDP over 285,643 million hours worked, or USD 97.05 per hour. https://doi.org/10.1787/b024d9e1-en Accessed 2026-09-26.
  28. NASA. Apollo 11 Mission Overview: duration 8 days, 3 hours, 18 minutes, 35 seconds, from launch on July 16, 1969 to splashdown on July 24, 1969. https://www.nasa.gov/history/apollo-11-mission-overview/ Accessed 2026-09-25.
  29. Hirshleifer, D. (February 11, 2013). Friends: The Complete Series [Blu-ray review]. High-Def Digest. Technical specifications for the Warner Home Video release of November 13, 2012 (236 episodes, ten seasons): “Length: 5400” minutes. https://bluray.highdefdigest.com/7254/friends_complete.html Accessed 2026-09-26.
  30. Andersen, J. J. (August 28, 2025). The State of US Marathons 2025. RunRepeat: the average U.S. marathon finish time in 2024 was 4:34. https://runrepeat.com/the-state-of-us-marathons-2025 Accessed 2026-09-25.
  31. Running times of the fourteen titles in the 2009 stereo remaster box set, from each album’s English Wikipedia entry: Please Please Me 31:59, With the Beatles 33:07, A Hard Day’s Night 30:09, Beatles for Sale 33:42, Help! 33:44, Rubber Soul 34:59, Revolver 35:01, Sgt. Pepper’s Lonely Hearts Club Band 39:36, The Beatles (stereo) 93:33, Yellow Submarine 39:16, Abbey Road 47:03, Let It Be 35:10, Magical Mystery Tour (LP) 36:35, Past Masters 93:29. https://en.wikipedia.org/wiki/The_Beatles_discography Accessed 2026-09-26.
  32. 14 CFR § 61.109(a): an applicant for a private pilot certificate (airplane, single-engine) must log at least 40 hours of flight time, including at least 20 hours of flight training from an authorized instructor and 10 hours of solo flight training. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D/part-61/subpart-E/section-61.109 Accessed 2026-09-25.
  33. The National (July 13, 2026). In it for the ultra-long-haul: World’s 5 longest non-stop flights and how Project Sunrise will top them: Singapore Airlines’ New York JFK–Singapore flight takes “about 19 hours and 15 minutes”; Qantas’s Project Sunrise is “now due to begin in October 2027.” https://www.thenationalnews.com/travel/2026/07/13/longest-flights-singapore-qantas-emirates/ Accessed 2026-09-26.
  34. Channel Swimming & Piloting Federation. Solo Swims Statistics (database compiled by Julian Critchlow): mean of 3,384 solo crossings from 1875 to 2025, computed from the published yearly average times and crossing counts. https://cspf.co.uk/solo-swims-statistics-2 Accessed 2026-09-25.
  35. Tolstoy, L. War and Peace, trans. Louise and Aylmer Maude (Project Gutenberg eBook #2600): 562,487 words; read at 260 words per minute, the average adult silent reading rate for English fiction in 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, 104047. https://doi.org/10.1016/j.jml.2019.104047 Accessed 2026-09-25.
  36. U-Pack. What Is the Best Driving Route From California To New York?: the route via Interstate 40 and Interstate 70 is “just under 2,800 miles,” with an “Estimated driving time: 41 hours.” https://www.upack.com/articles/what-is-the-best-driving-route-from-california-to-new-york Accessed 2026-09-26.
  37. Knechtle, B., Valero, D., Villiger, E., Thuany, M., Andrade, M. S., Cuk, I., Nikolaidis, P. T., Rosemann, T., & Weiss, K. (2024). Sex difference in IRONMAN age group triathletes. PLOS ONE, 19(10), e0311202: mean finish times of 12:37:49 for 553,608 men and 13:31:40 for 134,088 women in IRONMAN age-group races, 2002–2022. https://doi.org/10.1371/journal.pone.0311202 Accessed 2026-09-26.
  38. Royal Ballet and Opera (formerly the Royal Opera House). Opera Essentials: Ring Cycle: “If played continuously back-to-back, the four operas in Der Ring des Nibelungen would last 15 hours in duration.” https://www.rbo.org.uk/opera-essentials-ring-cycle Accessed 2026-09-25.
  39. U.S. Department of State, National Foreign Affairs Training Center. Foreign Language Training: Spanish is a Category I language, 30 weeks to an integrated score of 3 (speaking and listening) on the Interagency Language Roundtable scale, with a typical week of 23 hours in class. https://www.state.gov/national-foreign-affairs-training-center/foreign-language-training Accessed 2026-09-25.
  40. 29 U.S.C. § 207(a)(1) (Fair Labor Standards Act): no employer shall employ a covered employee “for a workweek longer than forty hours” unless paid at least one and one-half times the regular rate for the excess hours. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title29-section207&num=0&edition=prelim Accessed 2026-09-25.