How do you calculate the average daily amount for EPCRA Tier II?

For the EPCRA Tier II average daily amount, add up the amount of the chemical on site for each day it was there during the calendar year, then divide by the number of those days. That's the method in EPA's Tier II instructions, and the divisor is the count of days on site, which equals 365 in a non-leap year, or 366 in a leap year, for a chemical present every day. The result goes on the form as a range code from 40 CFR 370.43(a). The rule itself, 40 CFR 370.42(s)(7), asks for "an estimate (in ranges) of the average daily amount" and gives no formula.

In February, the environmental coordinator of a general contractor sits down with the delivery tickets from a bridge repainting job. Twelve thousand pounds of a coating solvent came on site in April and stayed at that level for 60 days. It sat at 6,000 pounds for 40 more, and the last of it left in mid-July. Add up the 100 daily amounts and divide by 365, and the Tier II average comes out near 2,630 pounds, range code 04. Divide by the 100 days the solvent was there, the way EPA's instructions say, and it's 9,600 pounds, code 05.

How do you calculate the average daily amount for EPCRA Tier II?

EPA puts the method in one sentence of its Tier II instructions. The May 2026 edition, page 14, under "Average Daily Amount Range Code," reads: "To do this, total all daily weights and divide by the number of days the hazardous chemical was present on site." The June 2017 edition has the same sentence on page 10, worded "the number of days the chemical was present on the site."

On a worksheet, that comes down to four steps:

1. Decide what one day's amount is. EPA doesn't define it (more on that below), so the convention is yours to set, and it holds for every day of the year.
2. Write down that amount, in pounds, for each day of the calendar year the chemical was on site. A volume becomes pounds through a density factor under Note 1 to 40 CFR 370.43(a).
3. Add the daily amounts and divide the total by the number of days on site.
4. Find the range the result falls in and enter its code from the 40 CFR 370.43(a) table, unless your SERC or LEPC asks for other codes or exact amounts under 40 CFR 370.43(b).

The days you divide by are the days the chemical was present, and that's also what the "Number of Days On-Site" box asks for. 40 CFR 370.42(s)(8) words it as "the maximum number of days that the hazardous chemical or mixture was present at your facility during the preceding calendar year." EPA's 2017 example uses its 315 days for both.

What does 40 CFR 370.42 require for the average daily amount?

Paragraph (s) of 40 CFR 370.42 opens with "For each hazardous chemical that you are required to report, you must:" and three of the items that follow are quantities:

• 40 CFR 370.42(s)(6) asks for "an estimate (in ranges) of the maximum amount of the hazardous chemical present at your facility on any single day during the preceding calendar year."
• 40 CFR 370.42(s)(7) asks for "an estimate (in ranges) of the average daily amount of the hazardous chemical present at your facility during the preceding calendar year."
• 40 CFR 370.42(s)(8) asks for "the maximum number of days that the hazardous chemical or mixture was present at your facility during the preceding calendar year."

The statute uses the same words. 42 U.S.C. 11022(d)(2)(C) calls for "An estimate (in ranges) of the average daily amount of the hazardous chemical present at the facility during the preceding calendar year." Under 40 CFR 370.45(a), the inventory is due "on or before March 1st of each year" and covers the hazardous chemicals present at your facility "during the preceding calendar year."

The regulation requires an estimated average in ranges but supplies no formula for calculating it. EPA’s Tier II form instructions supply the division by days on site. Keep the calculation with the inventory so the person certifying the report can explain how it was obtained.

The three numbers are owed for each hazardous chemical you have to report. Under 40 CFR 370.12(a), that's any chemical you must have an SDS for under OSHA's Hazard Communication Standard that is present at or above its threshold. Part 370 borrows OSHA's definition: in 40 CFR 370.3, a hazardous chemical is "any hazardous chemical as defined under 29 CFR 1910.1200(c)," minus the exclusions listed there. On a construction site, the Hazard Communication Standard applies through 29 CFR 1926.59, which says the requirements for construction work are "identical to those set forth at § 1910.1200 of this chapter."

The thresholds sit in 40 CFR 370.10, and they look at the amount present at any one time. For an extremely hazardous substance, it's 500 pounds or the threshold planning quantity, whichever is lower. For other hazardous chemicals, it's 10,000 pounds, except gasoline and diesel at a retail gas station, which get gallon thresholds of their own. And when your LEPC, SERC or the fire department with jurisdiction over your facility asks for Tier II information, 40 CFR 370.10(b)(2) puts the threshold for answering at zero. Whether a construction company files at all is the subject of EPCRA Tier II reporting for construction: do you need to file?

Where does the Tier II average formula come from?

It comes from EPA's instructions for the Tier II form, which sit outside the CFR. EPA's "Tier II Forms and Instructions" page (last updated June 22, 2026) posts two editions, and the report you're filing decides which one applies:

EPA's page labels the first "2017 to 2026 Tier II Form (for use through calendar year 2026, i.e., the report due by March 1, 2027)" and the second "2027 Tier II Form (for use starting in calendar year 2027, i.e., the report due by March 1, 2028)." A report filed by March 1, 2027 still runs on the 2017 instructions. Both editions give the same formula and print the same range table as 40 CFR 370.43(a).

EPA’s 2017 instructions work through a solvent held for 315 days. The total of its daily volumes is 4,536,000 gallons, giving an average of 14,400 gallons over those 315 days. The example then calculates the benzene component using a percentage of volume. For a mixture component on your own report, follow 40 CFR 370.14(c): multiply the component’s weight percent by the mixture’s weight in pounds. A percentage by volume is a different measurement. The 2026 instructions omit the worked average example.

At least one state manual repeats the federal sentence word for word. Ohio EPA's SERC compliance manual, revised 1/2026, says on page 16: "To do this, total all daily weights and divide by the number of days the chemical was present on the site." It gives no worked example either.

Why shouldn't you divide the average daily amount by 365?

EPA's instructions divide by the days the chemical was present, and 365 matches that for a full non-leap year. A chemical present throughout a leap year has 366 days on site. For anything that came and went, dividing by 365 spreads the stock over days it wasn't there and pulls the average down, sometimes into a lower range code.

Two cases, with our own arithmetic (these aren't EPA examples):

The codes come from the table in 40 CFR 370.43(a): 04 runs from 1,000 to 4,999 pounds, 05 from 5,000 to 9,999, and 06 from 10,000 to 24,999.

Look at the steady tank. A chemical that never dropped below 12,000 pounds comes out at about 3,300 pounds, code 04. EPA's range-code FAQ (last updated March 24, 2026) says why that matters to the people reading the form: "EPA recognizes that the actual amount of a hazardous chemical present at a facility is the most useful information for effective planning and response by the Local or Tribal Emergency Planning Committee (LEPC or TEPC)."

In the drawn-down tank, the maximum and the average carry different codes, 06 and 05, because 40 CFR 370.42(s)(6) and (s)(7) ask for two separate estimates.

What counts as one day's amount on a Tier II report?

No federal text says. The definitions in 40 CFR 370.3 define neither a day nor an amount. EPA's "total all daily weights" leaves the daily weight undefined too, and nothing tells you whether it's the balance at quitting time or the highest balance of the day. The 2017 example speaks of "the sum of the daily volume levels in the tank," which implies one level per day without saying which. Neither edition specifies an end-of-day reading or a daily peak. Document the convention you use and check it against your state’s instructions.

The choice moves the number. Take a day that starts with 3,000 pounds in the tank. A 9,000-pound delivery at 10 a.m. brings it to 12,000, and the crew draws it down to 8,000 by quitting time. That day's closing balance is 8,000 pounds and its highest balance is 12,000. A day's highest balance is never below any other balance that day, so an average built on daily peaks can't come out lower than one built on closing balances. Close to a range boundary in 40 CFR 370.43(a), it can land a code higher.

The maximum has a firmer anchor. 40 CFR 370.42(s)(6) measures it "on any single day," the statute says "at any time," and the May 2026 instructions say "at any one time." The largest daily peak of the year fits all three wordings.

So pick a convention and use it for every chemical, with a line at the top of the worksheet that says what it is. 40 CFR 370.42(s)(7) asks for an estimate, and under 40 CFR 370.42(a) the owner or operator certifies that "all information included in the Tier II submission is true, accurate, and complete." Whoever signs should be able to say how the daily amounts were taken.

What counts as a day on site for Tier II?

40 CFR 370.42(s)(8) wants the number of days the chemical "was present at your facility," and neither the rule nor the instructions say what to do with a partial day. Think of a drum delivered at 3 p.m., or a load received and used up before the end of the shift. The rule counts days within a calendar year, and no text says when a day starts or which time zone it runs in.

Whatever rule you set for the daily amount, use the same days for the divisor and for the Number of Days On-Site box, the way EPA's 2017 example uses its 315 days for both. The days go on the form as a number. The 40 CFR 370.43(a) codes cover only the maximum amount and the average daily amount, and the 2017 example says "Enter 315 in the space provided."

Which range code goes on the Tier II form?

The code comes from 40 CFR 370.43(a), which opens: "Except as provided in paragraph (b) of this section, you must use the following codes to report the maximum amount and average daily amount when reporting Tier I or Tier II inventory information:"

Both editions of EPA's instructions print the same thirteen ranges. EPA's range-code FAQ states the federal floor: EPA "only requires the owner or operator to enter ranges for both the maximum amount and average daily amount."

Your state can ask for more. 40 CFR 370.43(b) lets a SERC or LEPC "provide other range codes for reporting maximum amount and average daily amount or may require reporting of specific amounts," provided the ranges "are not broader than the ranges in paragraph (a)." The 2017 instructions say so in a boxed note on page 10: "Your state may require you to report exact amount for maximum amount and average daily amount rather than in ranges. Check with your state for specific requirements." And 40 CFR 370.42 itself warns that "Some states may require you to use a state reporting format including electronic reporting and certification for submitting your hazardous chemical inventory." Keep the pounds you computed next to each code, because an exact-amount state wants the pounds.

How do gallons and mixtures enter the average daily amount?

Every daily amount has to be in pounds before you add them up. Note 1 to 40 CFR 370.43(a) says: "To convert gas or liquid volume to weight in pounds, multiply by an appropriate density factor." When the SDS lists no density, EPA's FAQ (last updated April 14, 2026) says the owner or operator "may estimate the weight based on the density of water (8.3 pounds per gallon, or 2.2 pounds per liter), when making EPCRA §312 threshold determinations." That FAQ covers a liquid and the threshold determination. It says nothing about the range code you report.

For a mixture reported as a whole, 40 CFR 370.42(s)(7) asks for "an estimate of the average daily amount of the mixture." To report a component instead, 40 CFR 370.14(c) gives the method: "multiply the concentration of the hazardous chemical component (in weight percent) by the weight of the mixture (in pounds)." The same paragraph lets you leave out a component at 1% or less, or 0.1% or less for a carcinogen. EPA's mixtures FAQ (last updated April 14, 2026) adds: "When the composition of a mixture is unknown, facilities should report on the mixture as a whole, using the total quantity of the mixture." Whichever option you choose, 40 CFR 370.14(b) says it "must be consistent for both SDS and inventory reporting, unless it is not possible to do so." For an extremely hazardous substance inside a mixture, 40 CFR 370.42(s)(6) adds "the total amount of each EHS in that mixture" to the maximum. 40 CFR 370.42(s)(7) asks for no average per EHS.

Which average daily amount claims hold up against the text?

How do you get the three Tier II numbers from a stock log?

A spreadsheet works if somebody enters one amount for every day the chemical is on site and keeps the same convention all year. A movement log works too. Once every movement carries a date, the balance on any day can be rebuilt and the three numbers follow from it. If your inventory still lives in a spreadsheet, start from our chemical inventory template for OSHA and Tier II.

HazComFast keeps that movement log for you, one product at a time on each jobsite. Deliveries, consumption, disposals, transfers to another jobsite and counts all land in the same history, each with its date and time, and every line keeps the balance it left behind. Containers carry printed labels and get scanned into their storage place, from a building down to a cabinet or a conex box. When a planned count closes, each counted quantity becomes the new balance.

In February, nobody rebuilds the year by hand. Open the Stock tab for the jobsite, pick the reporting year under "Figures for," and each product row already shows its "Max daily amount," its "Average daily amount" and its "Days on site," in pounds. The line under the year says it plainly: "No figure is typed by hand."

A day's amount is the highest balance of that day, counted from midnight to midnight in your organization's time zone, so the delivery day above counts as 12,000 pounds. The average divides by the days the product was actually on site, never by 365. Those are HazComFast's conventions for what EPA's instructions leave open, and they apply the same way to every product, every year.

Volumes become pounds through the density saved for the product. Until one is saved, the figure is computed with the density of water and flagged with an asterisk, which tells you exactly which rows to firm up before March 1. When a product's history on the jobsite starts after January 1, its row says "Tracked since" with the date, so the figures show where the record begins.

The figures belong to one product on one jobsite. 40 CFR 370.42(s) asks about amounts "present at your facility," and 40 CFR 370.3 defines a facility as the buildings, equipment, structures and other stationary items "located on a single site or on contiguous or adjacent sites" and owned or operated by the same person. That definition doesn't settle by itself whether a given jobsite is a facility of its own, so match your jobsites to your facilities before a number goes on the form. The signature stays with the company: under 40 CFR 370.42(a), the owner or operator, or the officially designated representative, certifies the submission.

Related reading: EPCRA Tier II reporting for construction: do you need to file? · Chemical inventory: OSHA and Tier II template