One US gallon is exactly 128 US fluid ounces, 8 pints or 4 quarts. NIST Handbook 44, Appendix C defines the US gallon as 231 cubic inches and lists 128 US fluid ounces per gallon as exact. Every row below follows from those two definitions. The only rounding is in the decimals shown, and the table marks where that happens.
Unit equivalents (all exact)
| Unit | US fl oz | Pints | Quarts | Gallons |
|---|---|---|---|---|
| 1 fl oz | 1 | 0.0625 | 0.03125 | 0.0078125 |
| 1 pint | 16 | 1 | 0.5 | 0.125 |
| 1 quart | 32 | 2 | 1 | 0.25 |
| 1 gallon | 128 | 8 | 4 | 1 |
The Appendix C factors for pints (0.125 gal) and quarts (0.25 gal) match these values. A conversion table is read in one direction. To go from a smaller unit to a larger one, divide (fl oz ÷ 128 = gal). To go the other way, multiply (gal × 128 = fl oz).
Common container sizes in every unit
The container sizes below are nominal. Read the actual size from the label, and measure the fill level if a container is partly used.
| Container | fl oz | Pints | Quarts | Gallons | Liters (rounded to 3 decimals) |
|---|---|---|---|---|---|
| 16 fl oz bottle | 16 | 1 | 0.5 | 0.125 | 0.473 |
| 32 fl oz bottle | 32 | 2 | 1 | 0.25 | 0.946 |
| 1 gal | 128 | 8 | 4 | 1 | 3.785 |
| 3.5 gal | 448 | 28 | 14 | 3.5 | 13.249 |
| 5 gal | 640 | 40 | 20 | 5 | 18.927 |
| 20 gal | 2,560 | 160 | 80 | 20 | 75.708 |
The liter column is rounded. It comes from 231 in³ × 16.387064 cm³/in³ = 3,785.411784 cm³ per gallon, so 1 gal = 3.785411784 L exactly. NIST lists the gallon as "3.785 liters" in rounded form.
How many of one container fit in another
Read the table as "one row-volume equals this many of the column container." Values are rounded to four decimals where they do not terminate.
| Volume | 16 fl oz bottles | 32 fl oz bottles | 1 gal | 3.5 gal | 5 gal | 20 gal |
|---|---|---|---|---|---|---|
| 16 fl oz | 1 | 0.5 | 0.125 | 0.0357 | 0.025 | 0.00625 |
| 32 fl oz | 2 | 1 | 0.25 | 0.0714 | 0.05 | 0.0125 |
| 1 gal | 8 | 4 | 1 | 0.2857 | 0.2 | 0.05 |
| 3.5 gal | 28 | 14 | 3.5 | 1 | 0.7 | 0.175 |
| 5 gal | 40 | 20 | 5 | 1.4286 | 1 | 0.25 |
| 20 gal | 160 | 80 | 20 | 5.7143 | 4 | 1 |
A result such as 1.4286 five-gallon pails per 3.5 gallons never comes out as a whole container. For ordering, round up to whole containers. For mixing, keep the unrounded volume.
Volume, weight and other gallons
Fluid ounces measure volume. Avoirdupois ounces measure mass. Converting between them needs the product's density, which is normally in SDS Section 9. Use mass = volume × density, in consistent units. Do not treat 1 fl oz as 1 oz of weight for a concentrate, because only water comes close.
The US gallon is not the imperial gallon. NIST Appendix C lists the British imperial gallon as 277.42 in³, 4.546 L and 160 imperial fluid ounces, against 128 for the US gallon. A non-US spec sheet or imported dispenser may use imperial units. Check the unit before applying any figure to this table.
This table converts volume only. Concentration units are separate. ppm is mg/L, and percent by volume is not percent by weight. Chlorine available as free chlorine and quaternary ammonium active-ingredient concentration are not interchangeable either. Never use this table to convert between those.
Where rounding enters
Exact conversion and measuring practice are different things. A 32 fl oz bottle at 1:64 needs exactly 0.5 fl oz of concentrate under one convention, and about 0.492 fl oz under another.
The label wording decides which convention applies. The Batch Mixing Table Generator makes you choose between them: "1:64 means 1 part concentrate in 64 parts of finished solution" or "1:64 means 1 part concentrate plus 64 parts of water". Its default result, 0.250 fl oz for a 16 fl oz bottle and 2.000 fl oz per gallon, matches the first (total-solution) convention.
| Container | Total-solution convention (÷ 64) | Concentrate + water convention (÷ 65) |
|---|---|---|
| 32 fl oz bottle | 0.500 fl oz | 0.492 fl oz |
| 1 gal | 2.000 fl oz | 1.969 fl oz |
| 20 gal | 40.0 fl oz | 39.4 fl oz |
The per-gallon formula is concentrate (fl oz per gal) = 128 ÷ N for the total-solution convention, or 128 ÷ (N + 1) for the concentrate-plus-water convention, where N is the second number in the label ratio. The 20 gal row is 2,560 ÷ 64 = 40 and 2,560 ÷ 65 = 39.38.
Rounding 0.492 up to a convenient 0.5 fl oz makes the mix about 1.6% stronger than the second convention calls for (0.5 ÷ 0.4923 = 1.0156). Whether that matters depends on the label. For a disinfectant or sanitizer, the label's dilution governs, and rounding is not a decision to make from this table.
Worked example: a partly used 5 gal pail
These inputs are assumed. The real dilution ratio and pail size come from the product label. The fill level comes from your own measurement.
- Pail: nominal 5 gal, with 3.2 gal remaining by measurement
- Label dilution: 2 fl oz of concentrate per gallon of finished solution, which is 1:64 on the total-solution convention (assumed)
Method 1 (convert to fl oz first): 3.2 gal × 128 = 409.6 fl oz. Then 409.6 ÷ 2 = 204.8 gal of finished solution.
Method 2 (work in gallons): 1 gal of concentrate makes 64 gal of solution (128 ÷ 2), so 3.2 × 64 = 204.8 gal.
Cross-check: 204.8 gal × 2 fl oz = 409.6 fl oz, which matches the concentrate in the pail. The pail is 64% full (3.2 ÷ 5). In 32 fl oz bottles, 409.6 fl oz is 12.8 bottles, so it is 12 full bottles plus 0.8 of one.
Pour volume is theoretical use. Spillage, line purging, over-pouring and dispenser error all raise real use above it. Treat them as a separate entered allowance. Do not fold them into the conversion.
Using the conversion in the calculators
Each calculator takes volumes in specific units, so check the unit on every field:
- Open the Batch Mixing Table Generator to build a chart for 16 and 32 fl oz bottles, 1 and 3 gal buckets and a 20 gal tank from one ratio. It does not include 3.5 or 5 gal sizes, so use the tables above to place those.
- Open the Spray Bottle Coverage Calculator takes bottle size in fl oz (range 1–128) and coverage in sq ft per gal. For example, a 32 fl oz bottle at an assumed 1,000 sq ft/gal covers 250 sq ft (0.25 gal × 1,000), and it rounds the bottle count up.
- Open the Machine Tank Fill Calculator takes tank capacity in gallons. It reports concentrate per tank in fl oz and for the whole floor in gal, so convert between them with the factor of 128.
- Open the Mop Bucket Coverage Calculator for bucket counts and concentrate per bucket.
For the process side, including how to keep a mixing chart tied to one product, ratio and date, see Building a Repeatable Mixing Chart for Bottles, Buckets, and Tanks. Operator manuals, not sales sheets, give the real tank capacity. The label and SDS always take precedence over any figure derived here.