Water Intake Calculator for Work in the Heat
OSHA and NIOSH guidance is about one cup of water every 15 to 20 minutes during moderate work in moderate heat. This calculator turns that into a per-hour, per-shift and whole-crew number you can load on the truck, and flags the two published upper limits: 6 cups in an hour and 12 quarts in 24 hours.
Water per worker, for the whole time in the heat
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Results are estimates for planning purposes and do not replace a competent person's evaluation or an engineer's design. Follow the OSHA standards that apply to your work and your employer's written program.
The published numbers, and where each one comes from
| Number | Source | What it is |
|---|---|---|
| 1 cup every 15-20 min | OSHA-NIOSH InfoSheet 3438 | Guidance for moderate activity in moderately hot conditions |
| 6 cups per hour | NIOSH, Working in Heat | Upper limit on fluid intake in any one hour |
| 12 quarts (48 cups) / 24 h | OSHA-NIOSH InfoSheet 3438 | Upper limit on total daily intake |
| 1 quart per worker per hour | OSHA proposed heat rule | Proposed supply requirement — how much has to be available, not how much a person must drink |
| 50-60 °F | OSHA Heat Stress Guide | Water temperature people will actually drink |
Potable drinking water is already required on construction sites by 29 CFR 1926.51, and in general industry by 1910.141, whether it is hot out or not. There is no final federal heat standard.
What makes the plan fail on a real jobsite
- Water that is far away is water that is not drunk. OSHA asks for it in convenient, visible locations close to the work area — not at the gang box three floors down.
- Warm water gets skipped. Cool, palatable, odor-free is the standard; ice in the cooler is a hydration control, not a comfort item.
- Thirst is a late signal. OSHA's guide says thirst cannot be relied on as a guide to the need for water, so the crew drinks on the clock, not on the feeling.
- Individual cups. A shared dipper is a sanitation problem; NIOSH's guidance is individual drinking cups.
- Clear or lightly colored urine is the check OSHA tells employers to teach. It costs nothing and it works.
- More is not better. Past 6 cups in an hour or 12 quarts in a day, the risk stops being dehydration.
How it's calculated
- Cups per hour
cups/hour = 60 / drinking interval (min)15-minute interval = 4 cups per hour; 20-minute interval = 3 cups per hour.- Water per worker per hour
volume/hour = cups/hour × cup sizeFour 8 fl oz cups per hour is 32 fl oz — one quart per hour.- Water per worker per shift
volume/shift = volume/hour × hours in the heat- Water to bring for the crew
crew volume = volume/shift × number of workersDivide by 128 for US gallons, or by 1,000 for liters if you are working in metric.- Published upper limits
cups/hour ≤ 6 · total intake ≤ 12 quarts (48 cups) in 24 hoursNIOSH: fluid intake should generally not exceed 6 cups per hour. OSHA-NIOSH InfoSheet 3438: workers should generally not drink more than 12 quarts (48 cups) in a 24-hour period; if more replacement is needed, a more comprehensive heat illness prevention program may be warranted.
Frequently asked questions
OSHA and NIOSH guidance is about 1 cup every 15 to 20 minutes during moderate work in moderately hot conditions — 3 to 4 cups, or 24 to 32 fluid ounces, per hour. Four 8-ounce cups an hour comes to exactly one quart, which is the supply figure in OSHA's proposed heat rule.
Yes. The OSHA-NIOSH InfoSheet says workers should generally not drink more than 12 quarts, or 48 cups, in a 24-hour period, and NIOSH puts a ceiling of about 6 cups in any one hour. Drinking past those amounts can dilute the body's sodium. If a job really needs more fluid than that, the InfoSheet says a more comprehensive heat illness prevention program is warranted.
Multiply the per-worker shift volume by the crew size and divide by 128. A crew of six drinking a quart an hour for an 8-hour shift needs 12 gallons on site — before you count what gets spilled, used for washing, or drunk by anyone who shows up unplanned.
Yes, potable drinking water is already required on construction sites by 29 CFR 1926.51 and in general industry by 1910.141, independently of heat. OSHA's proposed heat rule would go further and require a supply sufficient for 1 quart per employee per hour, kept cool, at no cost to the worker. That rule is not final.
OSHA's guidance is that regular meals and snacks replace the salt and electrolytes lost in sweat as long as enough water is being drunk, and that electrolyte drinks are usually not necessary. NIOSH adds that when sweating lasts several hours, sports drinks with balanced electrolytes are appropriate. OSHA also says to avoid alcohol and drinks high in caffeine or sugar, and workers should avoid salt tablets.
OSHA's heat stress guidance asks for cool water — 50 to 60 °F if possible — with a palatable, odor-free taste, in convenient visible locations close to the work area. Water people do not want to drink does not get drunk.
No. OSHA's guide states plainly that thirst cannot be relied on as a guide to the need for water, which is why the guidance is a clock interval and not a feeling. Workers should be told to drink small amounts frequently, before they are thirsty.
Sources & references
- OSHA-NIOSH InfoSheet — Protecting Workers from Heat Illness (OSHA 3438, DHHS/NIOSH 2011-174): 1 cup every 15 to 20 minutes; no more than 12 quarts (48 cups) in 24 hours
- NIOSH — Working in Heat (hydration): fluid intake should generally not exceed 6 cups per hour; sports drinks for prolonged sweating
- OSHA — Heat Stress Guide: water must be taken every 15 to 20 minutes in hot environments; cool water at 50-60 °F
- OSHA — Heat Injury and Illness Prevention proposed rule, regulatory text (supply sufficient for 1 quart per employee per hour)
- 29 CFR 1926.51 — Sanitation (potable water on construction sites)
Content checked against these sources — last reviewed August 28, 2026.