Convert fl oz to cups US fluid ounces ↔ US cups Free Online Secure
Type a value in US fluid ounces and read it in US cups at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
Nothing uploaded
Convert from US fluid ounces
Convert to US cups
Common values — Convert fl oz to cups (US fluid ounces ↔ US cups)
| fl oz | cup |
|---|---|
| 1 | 0.125 |
| 2 | 0.25 |
| 3 | 0.375 |
| 5 | 0.625 |
| 10 | 1.25 |
| 20 | 2.5 |
| 50 | 6.25 |
| 100 | 12.5 |
Where these units come from
The litre has an awkward history. From 1901 it was defined as the volume of one kilogram of pure water at its densest, which sounds elegant but came out at 1.000028 cubic decimetres — close enough to be confusing and far enough to spoil careful work. In 1964 the definition was abandoned and the litre became exactly one cubic decimetre, which it has been ever since. The gallon has a messier story still: the US gallon descends from the English wine gallon of 231 cubic inches, while Britain redefined its own in 1824 as the volume of ten pounds of water. Nobody reconciled the two, so a US gallon is 3.785411784 litres and an imperial gallon 4.54609 — about a fifth larger. The gallon, pint, cup, fluid ounce and spoons on this page are the US ones.
Where you meet them
Millilitres and litres run through daily life almost invisibly: bottles, fuel, paint, dosage, the capacity of a kettle. Cubic metres belong to water bills, concrete, shipping and the air a ventilation system has to move. Cubic centimetres name engine displacement, cubic feet appear in freight and in appliance capacities, and cups and spoons live almost entirely in recipes — which is exactly where the difference between a US cup and a metric one quietly ruins a cake.
Questions people ask
Is a fluid ounce a measure of weight?
No, it is a measure of volume, even though ounce also names a weight. A US fluid ounce is 29.5735 millilitres; the imperial one is slightly smaller, at 28.4131. The shared name is a historical accident, and for water the two roughly match, since a fluid ounce of water weighs close to an ounce.
Are cups and spoons the same everywhere?
No, and this catches people out. The cup used here is the US one, 236.588 ml; a metric cup is 250 ml and an Australian one the same. The tablespoon here is 14.787 ml, while the metric tablespoon is 15 ml and the Australian one 20 ml. For a cake the difference rarely matters, but for yeast, salt or baking powder it does — when a recipe is precise, check whose spoon it means.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
How many loads in the bottle: laundry and cleaning liquids in cups
The laundry detergent bottle says 100 fluid ounces, the cap is marked in fractions of a cup, and the label promises 50 loads. The three figures hang together once you convert fl oz to cups: divide the ounces by 8, since a cup holds eight fluid ounces. A 100 ounce bottle is 12.5 cups, and at a quarter cup a load, 2 ounces, that is 50 loads. This page divides as you type, and the text below goes round the laundry room and the cleaning cupboard, showing how ounces on the bottle turn into cups in the cap and into cost per use.
The page covers the rule with examples, a note on each unit, a comparison, a tour of household liquids and the slips to avoid. All arithmetic happens in your browser; nothing you enter is sent anywhere. Always follow the label and never mix cleaning products.
How to convert fl oz to cups: divide by 8
The rule
A US cup is exactly 8 fluid ounces, so one fluid ounce is an eighth of a cup. To convert fl oz to cups, divide the ounces by 8, or multiply by 0.125. So 8 fl oz is 1 cup, 20 fl oz is 2.5 cups, 64 fl oz is 8 cups and 100 fl oz is 12.5 cups. In the other direction, multiply cups by 8.
Worked examples
A 50 ounce bottle of detergent is 6.25 cups. A 32 ounce bottle of spray cleaner is 4 cups. A 24 ounce bottle of dish soap is 3 cups. A 121 ounce jug of bleach is 15.1 cups, nearly a gallon, which is 16 cups.
Why 8 and not 16
A pint holds 16 fluid ounces and a quart 32. A cup holds only 8. Dividing by 16 would give half the true number of cups, and promise twice as many loads.
A quick sanity check
The cup is the larger unit, so the number shrinks eightfold. If your “convert fl oz to cups” calculation result shrank by half or fourfold, you used the pint or quart factor.
The fluid ounce
An eighth of a cup
The US fluid ounce is 29.57 millilitres. It is the unit on every bottle of household liquid in the United States, together with millilitres on newer labels. It measures volume, unlike the ounce on a scale.
Where it appears
Detergents, cleaners, drinks, cosmetics and medicines.
The cup
Eight fluid ounces
The US cup is 236.6 millilitres. Detergent caps and measuring jugs use cups and fractions of cups, because they are easier to read than ounces for small doses. A quarter cup is two ounces, a half cup four.
Where it appears
Caps, jugs, recipes and instructions.
Fluid ounce and cup compared
A cup holds 8 fluid ounces. Bottles are sized in ounces and doses in cups or fractions: a quarter cup per load, a half cup of bleach, a third of a cup of softener. A bottle of 64 ounces gives 8 cups, which at a quarter cup a load makes 32 loads. The label's number of loads is just the bottle's cups divided by the dose.
The factor 8 is exact. The only trap is mixing fluid ounces with ounces of weight, which appear on some products.
Where the conversion appears
Laundry detergent
Common bottle sizes are 50, 64, 100 and 150 fluid ounces, 6.25, 8, 12.5 and 18.75 cups. A concentrated detergent might call for 2 ounces, a quarter cup, a load, and a regular one for 4 ounces, half a cup. A 100 ounce bottle then gives 50 or 25 loads. Whenever you convert fl oz to cups, the loads per bottle follow from the dose, so do the sum before buying.
Bleach, softener and boosters
A jug of bleach of 121 ounces holds 15.1 cups; at half a cup, 4 ounces, a load, it gives about 30 loads. A fabric softener of 64 ounces gives 8 cups, which at a third of a cup is 24 loads. Boosters and stain removers come in smaller bottles of 24 or 32 ounces, 3 or 4 cups.
Dish soap and surface cleaners
Dish soap comes in 24 or 38 ounce bottles, 3 or 4.75 cups. A spray cleaner holds 32 ounces, 4 cups. Concentrated cleaners are diluted at 1 to 1 or 1 to 10, so a ready-to-use bottle of 32 ounces may need 3 ounces, 0.375 cups, of concentrate and 29 of water. The label gives the ratios.
Cost per load
A 100 ounce bottle of detergent at 12 dollars, with 50 loads of 2 ounces, costs 24 cents a load. A 150 ounce bottle at 16 dollars with 75 loads is 21 cents. The bigger bottle is cheaper per ounce, 10.7 cents against 12. Comparing the cost per cup, 96 cents against 85, tells the same story: the bottle with the lower price per cup is the better value if the doses are equal.
Car care liquids
Windscreen washer fluid comes in 128 ounce jugs, 16 cups, a gallon. Car wash soap is diluted at 1 ounce per gallon, so a 32 ounce bottle makes 32 gallons. Wax and polish come in small bottles of 16 ounces, 2 cups. Many car care instructions mix ounces, cups and gallons, and a quick conversion keeps the units straight.
Shampoo, soap and personal care
A shampoo bottle of 12 ounces holds 1.5 cups, and a family-size bottle of 33 ounces holds 4.1 cups. Hand soap refills come in 32 ounces, 4 cups. A pump of hand soap dispenses about 0.05 ounce, so a bottle of 8 ounces, a cup, gives 160 pumps. Personal care products are compared by price per ounce, a number easily converted to price per cup.
In a spreadsheet
Put ounces in column A and use =A2/8 in column B. For the reverse, =B2*8. A column with =B2/dose_in_cups gives loads per bottle, and =price/B2 gives price per cup. Format with one decimal for cups and two for prices, and keep the source column for audit.
Rounding
The factor is exact, so rounding is mainly about the loads. 12.5 cups at a quarter cup a load is exactly 50 loads, but 12.6 cups gives 50.4, which you count as 50. Round down loads, since the last one is not a full dose. Prices are rounded to the cent, and unit prices to a tenth of a cent for comparison.
A mental shortcut
Dividing by 8 is three halvings: 64 ounces, 32, 16, 8 cups. 100 ounces, 50, 25, 12.5 cups. For loads at a quarter cup, multiply the cups by 4: 12.5 cups gives 50 loads. For half a cup, multiply by 2. These two steps are all you need to check the number on a detergent label.
Reference values
4 fl oz is 0.5 cup, 8 fl oz is 1 cup, 12 fl oz is 1.5 cups, 16 fl oz is 2 cups, 32 fl oz is 4 cups, 50 fl oz is 6.25 cups, 64 fl oz is 8 cups and 100 fl oz is 12.5 cups. If you convert fl oz to cups and land far from this ladder, repeat the division.
Checking by reversing
To make sure your “convert fl oz to cups” calculation result is right, multiply it by 8. If 100 ounces gave 12.5 cups, then 12.5 times 8 returns 100. A second check is the size of the answer: it should be an eighth of the ounces. If it is half, you divided by 16.
Hand sanitiser and soap dispensers
A refill of 32 ounces, 4 cups, for a wall dispenser serves about 128 doses of a quarter ounce. A pump bottle of 8 ounces, a cup, serves 160 pumps. Facilities managers convert fl oz to cups and then calculate how many refills a building needs per month from the doses per day, and the bottle size in cups tells them how many rooms one refill stocks.
Pressure washers and mop buckets
A mop bucket of 3 gallons, 384 ounces, 48 cups, takes 2 ounces of floor cleaner, a quarter cup, at a typical dilution of one ounce per 1.5 gallons. A pressure washer detergent tank of 64 ounces, 8 cups, treats several jobs. Labels give ounces per gallon, and a conversion to cups lets the user fill a tank with a familiar measuring jug.
Cooking oil and kitchen liquids
A bottle of cooking oil of 48 ounces holds 6 cups. A recipe calling for a third of a cup of oil, 2.7 ounces, leaves 5.7 cups, enough for 17 such recipes. Kitchen liquids like vanilla extract come in 4 ounce bottles, half a cup, with recipes using a teaspoon, which is a sixth of an ounce. When you convert fl oz to cups for the bottle, the number of recipes follows.
Concentrated against regular
A regular detergent is dosed at half a cup, 4 ounces, a load, a concentrated one at a quarter cup, 2 ounces. A 100 ounce bottle of regular gives 25 loads, the same bottle of concentrate 50. A 50 ounce bottle of concentrate gives as many loads as a 100 ounce bottle of regular, so a smaller bottle can be better value despite a higher price per ounce.
Plant feed and houseplant care
Houseplant fertiliser concentrate comes in 8 ounce bottles, a cup, with a dose of a quarter teaspoon per quart of water. A bottle thus lasts for hundreds of waterings. The ounces on the label measure the liquid, while the dose is in much smaller units, so the cup is only the bottle's size. Even so, if you convert fl oz to cups for the bottle, you learn how much you are buying.
Water for the garden hose and watering can
A watering can of 2 gallons holds 256 ounces, 32 cups. A glass of water for a pot plant is 8 ounces, a cup. Watering 16 plants with a cup each uses half the can. People often think in cups for small plants and gallons for beds, and the factor of 8 ounces per cup is the bridge to the labels on fertiliser and cleaner bottles.
Essential oils and small bottles
Essential oils are sold in bottles of 0.5 or 1 fluid ounce, 15 or 30 millilitres, a sixteenth or an eighth of a cup. Recipes for diffusers use drops, around 600 to the ounce. A bottle of 1 ounce holds an eighth of a cup, and a recipe that needs a half cup of carrier oil is eight times the volume of the bottle. Handle concentrated oils with care.
Hot and cold water settings
Larger loads and heavily soiled clothes call for more detergent, perhaps 3 ounces, 3/8 cup, for a concentrated product. A machine with a drum of 4.5 cubic feet can take a full dose. The cap is marked with lines at different levels, and each line stands for an amount in ounces or cups. Reading the label's chart and the cap together avoids over-dosing.
Detergent pods and sheets
Pods and sheets avoid measurement altogether. A pod holds roughly 0.5 ounce of liquid, 15 millilitres, a tablespoon, in a water-soluble film. A box of 42 pods holds about 21 ounces, 2.6 cups. They are convenient but cost more per load and need keeping away from children. Comparing the cost of a pod with a quarter cup of liquid requires the liquid price per ounce.
Dishwasher products
A dishwasher detergent liquid of 75 ounces, 9.4 cups, gives 75 loads at an ounce a load, 0.125 cup. Rinse aid in a bottle of 16 ounces, 2 cups, lasts about 100 washes at a few drops each. Quantities are small, so the cap or dispenser is calibrated in teaspoons or tablespoons, the ounce divided further. The cups are only for the bottle.
Disinfectants and bleach dilution
Household bleach for disinfecting surfaces may be diluted at 1/3 cup of bleach per gallon of water, 2.7 ounces in 128, a ratio of 1 to 47. In a 32 ounce spray bottle, that is 0.67 ounce, a bit more than a tablespoon. Instructions on the bottle should be followed exactly, with ventilation and gloves, and bleach should never be mixed with ammonia, vinegar or other cleaners.
Vinegar cleaning solutions
A common homemade spray uses equal parts white vinegar and water. A 32 ounce bottle takes 16 ounces of each, 2 cups each. A mop bucket solution of 1 cup vinegar to a gallon of water is 8 ounces in 128, a ratio of 1 to 16. Vinegar is sold in 16, 32 and 128 ounce bottles, 2, 4 and 16 cups, and the quantities are easy to compute once ounces are turned into cups.
Fertiliser and garden sprays
Liquid fertiliser may call for 2 tablespoons per gallon of water, 1 ounce in 128, a ratio of 1 to 128. A bottle of 32 ounces, 4 cups, then makes 128 gallons. A 1 gallon sprayer takes 1 ounce, an eighth of a cup. Garden product labels give such rates per gallon, and conversion between ounces, tablespoons and cups makes it possible to use any measuring tool at hand.
Pool and hot tub chemicals
Liquid pool chlorine is dosed by the cup or quart for each 10,000 gallons. A bottle of 128 ounces holds 16 cups. A dose of 2 cups, 16 ounces, for 10,000 gallons would let the bottle treat 80,000 gallons in total. Always follow the product label, measure with dedicated tools and keep chemicals apart.
More values for convert fl oz to cups
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 fl oz = 0.0125 cup
- 0.5 fl oz = 0.0625 cup
- 3 fl oz = 0.375 cup
- 4 fl oz = 0.5 cup
- 7 fl oz = 0.875 cup
- 15 fl oz = 1.875 cup
- 20 fl oz = 2.5 cup
- 75 fl oz = 9.375 cup
- 200 fl oz = 25 cup
- 500 fl oz = 62.5 cup
- 2,000 fl oz = 250 cup
- 10,000 fl oz = 1,250 cup
Mistakes when you convert fl oz to cups
Dividing by 16
That is the factor for pints. For cups, divide by 8.
Mixing fluid and weight ounces
Some products, such as powders, are sold by weight. This page treats fluid ounces only.
Multiplying instead of dividing
The cup is the larger unit, so the number shrinks. If 100 oz became 800 cups, you multiplied.
Short answers
What is 1 fluid ounce in cups?
0.125 cups.
How do I convert fl oz to cups?
Divide by 8.
What is 1 cup in fluid ounces?
8 fluid ounces.
What does 100 fl oz come to in cups?
12.5 cups.
Does the page send my figure anywhere?
No, everything happens in your browser.
Related tools and a final note
Other volume converters sit nearby: Convert fl oz to ml, Convert fl oz to L, Convert pt to cups, Convert cups to pt, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert km² to ha. To go the other way, use Convert cups to fl oz.
To recap: you convert fl oz to cups by dividing by 8 and you write the unit beside the result. Everything is computed locally, with no account and no upload.