ml to oz Conversion Guide: US & UK Fluid Ounce Formulas, Charts & Scenarios (2026)
1 US fl oz = 29.5735 mL (NIST exact) and 1 UK fl oz = 28.4131 mL (BIPM exact). The FDA also permits 1 fl oz = 30 mL as a consumer-friendly rounding on nutrition labels (21 CFR 101.9). Those three factors handle almost every conversion between ml and oz you’ll run into.
US: fl oz = mL ÷ 29.5735 | mL = fl oz × 29.5735
UK: fl oz = mL ÷ 28.4131 | mL = fl oz × 28.4131
FDA label (approx): fl oz ≈ mL ÷ 30Equivalent multiplicative form: mL × 0.033814 = US fl oz (or mL × 0.035195 = UK fl oz).
Need a number now? → Open the free volume converter. It supports 15 units (US fl oz, Imperial UK fl oz, mL, cups, pints, gallons), runs entirely in your browser, and carries full IEEE 754 precision.
Below: the exact formulas (US, UK, FDA label), why the US and UK fluid ounces differ by 4%, when the 30 mL shortcut is safe, and how cooks, pharmacists and cosmetic brands hit the precision their field needs. JavaScript and Python snippets at the end include a roundtrip assertion.
The exact formulas: US, UK and nutrition-label rounding
Three numbers cover every conversion here — enough to convert milliliters to fluid ounces precisely for any real workflow. Keep the first two if you work across borders; the third is the FDA’s shortcut for shoppers.
US fluid ounce
1 US fl oz = 29.5735295625 mL, NIST exact. The number drops out of the 1959 International Yard and Pound Agreement plus the definition 1 US gallon = 231 cubic inches = 3785.411784 mL. Divide by 128 fl oz per US gallon and you get the eight-digit factor. Handbook 44, which every legal-for-trade scale and meter in the US is calibrated against, publishes the same value.
UK (Imperial) fluid ounce
1 UK fl oz = 28.4130625 mL, BIPM exact, codified by the UK Weights and Measures Act 1985. The Imperial gallon is 4546.09 mL, subdivided into 160 UK fl oz (not 128). That is why a UK fluid ounce is smaller even though the Imperial gallon is larger.
FDA nutrition-label rounding
1 fl oz ≈ 30 mL. 21 CFR 101.9(b)(5)(viii) lets food and beverage labels use this rounding for serving sizes so shoppers can do the arithmetic without a calculator. The error is (30 − 29.5735) / 29.5735 = 1.44%. Fine for cereal boxes, wrong for prescription dosing.
Worked example: 500 mL in fl oz
500 mL ÷ 29.5735 = 16.9070 US fl oz
500 mL ÷ 28.4131 = 17.5975 UK fl oz
500 mL ÷ 30 = 16.6667 fl oz (FDA label approx)That is how the same 500 mL bottle gets labeled 16.9 fl oz on a US shelf, 17.6 fl oz in the UK, and simply 500 ml e on a European one. Skip the arithmetic with our volume converter whenever the label side of the factor matters.
Why US and UK fluid ounces differ: the 1824 split
Why US fl oz vs UK fl oz differ comes down to an 1824 treaty decision. Most articles quote “4% difference” and stop. The split is a historical artefact with a date and a statute behind it, and it still has consequences for anyone importing or relabeling today.
1824 Imperial Act: when Britain redefined the gallon
Before 1824 the British Empire used the Queen Anne wine gallon (231 cubic inches). The Weights and Measures Act 1824 replaced it with the Imperial gallon, defined as the volume of 10 lb of distilled water at 62 °F, or about 277.42 cubic inches. The United States, independent since 1776, kept the Queen Anne gallon. Two gallons from two countries, ever since.
1 US gallon = 3785.41178 mL1 Imperial gallon = 4546.09 mL(about 20% larger)
Fluid-ounce math
Each country subdivides its gallon differently:
- US:
1 gal = 128 fl oz → 1 fl oz = 3785.41178 ÷ 128 = 29.5735 mL - UK:
1 gal = 160 fl oz → 1 fl oz = 4546.09 ÷ 160 = 28.4131 mL
The UK fluid ounce is smaller because the gallon is divided into more of them, not because the Imperial system runs on a different base.
Which countries use which?
- US fl oz: United States, Liberia, Myanmar.
- Imperial fl oz: United Kingdom (pub pints, some beverage labels), Ireland, and legacy use in Canada, Australia, New Zealand, South Africa, India and Malaysia.
- Pure metric (mL/L): EU, China, Japan, Korea, most of Latin America, Africa and the Middle East.
The 4% that matters: real cases
- Pharma formulation: a
500 mLpediatric suspension prints as16.91 US fl ozon a US label and17.60 UK fl ozon a UK label, a0.69 fl ozgap. - Spirits import: UK-bottled whisky comes in
700 mL (70 cl). A US retailer relabels it as23.7 US fl oz, not25 UK fl oz. Assuming the numbers cross over costs the importer the right-hand digit on a duty declaration.
For the broader US/UK split across length, mass and volume, see the unit conversion complete guide.
Mental-math tricks: when × 30 is good enough
You don’t always need eight digits. The four methods below cover drinks, baking, dosing and cross-checks, with a clear line for when to switch to the precise factor.
Method 1: FDA rule, mL ÷ 30
Fast. Good for beverage labels and rough dosing estimates.
- 330 mL cola →
330 ÷ 30 = 11 fl oz(exact 11.16, error 1.4%). - 240 mL glass of water →
240 ÷ 30 = 8 fl oz(exact 8.11). - 500 mL bottle →
500 ÷ 30 ≈ 16.7 fl oz(exact 16.91).
Use this at the supermarket, the bar, or when reading a nutrition label across systems. Do not use it to prepare a compounded medication. This is the classic 30 ml to oz mental shortcut.
Method 2: precision formula, mL ÷ 29.5735 (US)
When the bill or the patient chart depends on the answer:
- 500 mL ×
(1 / 29.5735)=16.9070 US fl oz. - Reverse:
8 US fl oz × 29.5735 = 236.59 mL(one US cup).
This is the factor the volume converter uses internally, to the full fifteen significant digits of double-precision arithmetic.
Method 3: UK-aware, mL ÷ 28.4
Round to 28.4 for mental math on UK recipes or British Pharmacopoeia formulations.
- 568 mL (UK pint) →
568 ÷ 28.4 ≈ 20 UK fl oz(exact 20.00, by definition). - 170 mL →
≈ 6 UK fl oz(exact 5.98).
A UK baker working from a 1970s cookbook that quotes “6 fl oz of milk” should treat it as UK, not US. The US reading would over-pour by 4%. Use this whenever a recipe calls for ml to oz cooking conversion.
Method 4: reverse quick check
Any fl oz value × 30 should land close to the original mL. If the error stays under 2%, the 30 mL shortcut is safe for that scenario.
8 fl oz × 30 = 240 mL(exact 236.59, error 1.4%, OK for a coffee cup).0.5 fl oz × 30 = 15 mL(exact 14.79, error 1.4%, OK for a cough-syrup dose, but read the next section).
When to never use the × 30 shortcut
Some scenarios amplify a 1.4% error until it matters:
- Prescription dosing. mg/mL concentrations multiplied by small volumes. A 1.4% error on a 5 mL pediatric dose is 0.07 mL, which is a miscount in a 0.25 mL oral syringe.
- Chemistry. Molarity, titration and reagent prep. Lab-grade work uses
29.5735(or pure mL) by default. - Cross-border customs. Duty brackets cut at exact volumes, and the 1.4% can nudge a shipment into a higher tariff tier.
- Cosmetics fill-volume audits. 76/211/EEC (the “e-mark” directive) tolerates only
±1% or ±4.5 mL, whichever is greater. The 30 mL shortcut alone blows through that tolerance.
Quick reference charts: ml ↔ fl oz
Bookmark this section. All values use 29.5735 mL/US fl oz and 28.4131 mL/UK fl oz to four decimals.
Beverage and drink container chart
| mL | US fl oz | UK fl oz | Reference |
|---|---|---|---|
| 30 | 1.01 | 1.06 | espresso shot |
| 150 | 5.07 | 5.28 | small wine pour |
| 175 | 5.92 | 6.16 | standard UK pub wine |
| 200 | 6.76 | 7.04 | juice carton (small) |
| 240 | 8.12 | 8.45 | US legal cup (240 mL label cup) |
| 250 | 8.45 | 8.80 | metric cup (AU/NZ) |
| 330 | 11.16 | 11.62 | European soda can |
| 355 | 12.00 | 12.50 | US soda can (12 fl oz) |
| 500 | 16.91 | 17.60 | standard water bottle |
| 568 | 19.22 | 20.00 | UK pint (exact 20 UK fl oz) |
| 750 | 25.36 | 26.40 | standard wine bottle |
| 1000 | 33.81 | 35.20 | 1 litre |
Cooking and baking chart (US & UK)
| Measure | mL | US fl oz | Notes |
|---|---|---|---|
| 1 US tsp | 4.929 | 0.167 | rounded 5 mL for cooking |
| 1 US tbsp | 14.787 | 0.500 | rounded 15 mL |
| 1 US fl oz | 29.574 | 1.000 | |
| 1 US cup | 236.588 | 8.000 | customary |
| 1 US legal cup | 240.000 | 8.115 | FDA labels (21 CFR 101.9) |
| 1 metric cup | 250.000 | 8.454 | AU/NZ |
| 1 UK cup (hist.) | 284.131 | 9.608 | pre-metric British cookbooks |
| 1 Japanese 合 gō | 180.000 | 6.087 | rice and sake |
“1 cup” is not an international standard. A US recipe asking for 1 cup of milk expects 236.6 mL; an Australian cookbook expects 250 mL. The volume converter carries all four cup variants for this reason.
Pharmaceutical dosing chart (US fl oz, precise)
| mL | US fl oz | Clinical context |
|---|---|---|
| 2.5 | 0.0845 | half a teaspoon (pediatric) |
| 5.0 | 0.1691 | standard teaspoon dose |
| 7.5 | 0.2536 | 1.5 × teaspoon |
| 10.0 | 0.3381 | two-teaspoon dose |
| 15.0 | 0.5072 | one tablespoon (adult) |
| 30.0 | 1.0144 | one fluid ounce (roughly) |
| 120.0 | 4.0577 | small suspension bottle |
| 240.0 | 8.1154 | one US legal cup |
Since 2015 FDA guidance for non-prescription pediatric liquids has required mL on dosing devices, not teaspoons, tablespoons or fluid ounces. ISMP reports document the reason: teaspoon-to-mL mis-reads caused thousands of accidental overdoses per year.
Cosmetics and perfume fill chart
| mL | US fl oz | Regulatory note |
|---|---|---|
| 15 | 0.51 | serum / sample size |
| 30 | 1.01 | 1 US fl oz travel jar |
| 50 | 1.69 | standard boutique fragrance |
| 75 | 2.54 | eau de toilette |
| 100 | 3.38 | TSA carry-on maximum (3-1-1 rule) |
| 200 | 6.76 | body lotion standard |
| 500 | 16.91 | salon-size shampoo |
US FDA (21 CFR 701) allows dual labeling (3.4 fl oz (100 mL)); EU Regulation 1223/2009 accepts only metric (100 ml e); China GB/T 7718 requires Chinese-language metric (100 毫升).
Weight units have their own US/UK split. See the kg to lbs conversion guide for the mass-side story, including the 9.7% gap between avoirdupois and troy ounces.
5 real-world scenarios where ml ↔ fl oz matters
The formula is trivial. The scenario is where errors hide. Five situations cover most of the real cost.
1. Cooking: adapting US recipes in metric kitchens
American food blogs assume US cup = 236.6 mL, but many international measuring cups land on 240 mL or 250 mL. That is a 1.4–5.7% drift per cup, invisible in soups and stews and lethal in macarons. For savoury cooking, round 1 cup ≈ 240 mL and move on. For baking, abandon volume entirely and weigh in grams. For pouring work (oils, syrups, stocks), the volume converter gives exact mL regardless of which cup a recipe assumes.
2. Beverage labeling: 12 fl oz soda can in the EU
A US 12 fl oz soda can holds 12 × 29.5735 = 354.88 mL. The EU edition usually prints 355 mL (rounded up by 0.12 mL, inside the 76/211/EEC e-mark tolerance of ±1% or ±4.5 mL). Bottled water goes the other way: a 1 L Evian is exactly one litre, but the US edition prints 33.8 fl oz (rounded from 33.814). The “12 fl oz ≈ 350 mL” shortcut you see in casual writing is wrong by more than 4 mL.
3. Pharmaceutical dosing: why the FDA phased out fl oz
For non-prescription pediatric liquids (acetaminophen, ibuprofen, antihistamines), the FDA has required mL-only dosing devices since 2015. Infant acetaminophen is typically 160 mg / 5 mL. A caregiver who reads “one teaspoon” and grabs a kitchen teaspoon delivers anywhere from 3 to 7 mL, up to 40% off on a drug whose hepatotoxic threshold is tight. Every bottle now ships with a 5 mL oral syringe graduated in 0.25 mL increments, with the dose labeled in mL only. The volume converter carries the precise 29.5735 factor so legacy fl oz records still reconcile with mL-first charts.
4. Cosmetics import: a 100 ml perfume bottle across regulations
One bottle, four regimes:
- US FDA accepts
3.4 fl oz (100 mL)dual labeling (21 CFR 701). - EU 1223/2009 accepts only
100 ml e. - China GB/T 7718 requires Chinese-language metric:
100 毫升. - TSA enforces the
3-1-1 rule: carry-on liquids ≤100 mL(3.4 fl oz). The 100 mL figure is the real limit. A3.5 fl ozbottle is 103.5 mL and gets confiscated.
Brands sell a single primary container at 100 mL and print region-specific labels around it. A compliance team uses the volume converter to verify each secondary unit before the sticker is cut.
5. Home brewing and spirits: 70 cl, 750 mL, 25.4 fl oz
Alcohol still uses cl (centilitres) heavily in Europe. 1 cl = 10 mL, so 70 cl = 700 mL:
- Wine bottle (standard):
750 mL = 75 cl = 25.36 US fl oz = 26.40 UK fl oz. - Whisky bottle: US market
750 mL, UK/EU market700 mL(70 cl). - Beer: US standard can
12 US fl oz = 355 mL; UK pint568 mL = 20 UK fl oz = 19.22 US fl oz. - Champagne half-bottle:
375 mL = 37.5 cl = 12.68 US fl oz.
A US bartender who reads “measure a 70 cl bottle” and reaches for the half-litre jug is off by 200 mL, a quarter of the bottle.
Common mistakes: fl oz vs oz, density traps
Weight oz vs volume fl oz: the biggest confusion
1 oz(avoirdupois, weight) =28.3495 g.1 US fl oz(volume) =29.5735 mL.
The numbers look alike, and they line up for water near 4 °C (density ≈ 1 g/mL). For any other liquid the two unit families decouple:
- Honey (
density ≈ 1.42 g/mL):8 fl oz → 336 g = 11.85 ozby weight. - Olive oil (
density ≈ 0.92 g/mL):8 fl oz → 218 g = 7.68 ozby weight. - Flour (
bulk density ≈ 0.55 g/mL):8 fl oz → 130 g = 4.59 ozby weight.
When a recipe says “8 oz honey”, it means weight. “8 fl oz honey” means a measuring cup. The weight converter handles the oz ↔ g side with the same NIST precision.
US fl oz and UK fl oz are not interchangeable
A UK label reading "6 fl oz" means 170.5 mL; a US label reading "6 fl oz" means 177.4 mL. The 4% gap compounds. A case of 24 × 200 fl oz shampoo interpreted in the wrong system drifts 230 mL per 24 bottles, enough to trigger a fill-volume rejection at customs.
”Cup” is not one unit
- US customary cup:
236.59 mL - US legal cup (FDA nutrition labels):
240 mL - Metric cup (AU, NZ):
250 mL - UK cup (historical, pre-metric cookbooks):
284.13 mL - Japanese cup (
1 合 / gō):180 mL
Five “cups” spanning 180–284 mL is a 58% range. Any recipe translated across regions should name the cup explicitly or drop cups entirely for grams and mL.
30 mL ≠ 1 fl oz in precision work
The 30 mL rounding is legally sanctioned (21 CFR 101.9) and fine at the breakfast table. It is not fine in a pharmacy’s sterile compounding room, a cosmetics QC lab, or an international trade contract. The rule is simple: if a 1.4% error would ever matter, write 29.5735.
Code examples: JavaScript and Python
The same factors that the volume converter uses drop straight into any codebase. Both snippets include a roundtrip assert that catches precision drift.
JavaScript
// NIST / BIPM exact factors
const ML_PER_US_FL_OZ = 29.5735295625;
const ML_PER_UK_FL_OZ = 28.4130625;
const mlToUsFlOz = (ml) => ml / ML_PER_US_FL_OZ;
const mlToUkFlOz = (ml) => ml / ML_PER_UK_FL_OZ;
const usFlOzToMl = (flOz) => flOz * ML_PER_US_FL_OZ;
const ukFlOzToMl = (flOz) => flOz * ML_PER_UK_FL_OZ;
// FDA nutrition-label approximation (21 CFR 101.9): 1 fl oz = 30 mL
const mlToFlOzNutritionLabel = (ml) => Math.round(ml / 30);
console.log(mlToUsFlOz(500)); // 16.907011350921895
console.log(mlToUkFlOz(500)); // 17.597539863927616
console.log(mlToFlOzNutritionLabel(500)); // 17 (consumer-friendly)
// Roundtrip sanity check — should be within machine epsilon
const back = usFlOzToMl(mlToUsFlOz(500));
console.assert(Math.abs(back - 500) < 1e-10, "US fl oz roundtrip drift");Keep ML_PER_US_FL_OZ and ML_PER_UK_FL_OZ as the single source of truth. Never inline 29.5735 in a second file. The day one gets corrected to the full fifteen-digit value and the other doesn’t, you have a silent rounding bug.
Python (pandas batch conversion + roundtrip assert)
import pandas as pd
ML_PER_US_FL_OZ = 29.5735295625 # NIST exact
ML_PER_UK_FL_OZ = 28.4130625 # BIPM exact
us_fl_oz_to_ml = lambda oz: oz * ML_PER_US_FL_OZ
df = pd.DataFrame({"ml": [30, 100, 250, 500, 750, 1000]})
df["us_fl_oz"] = df["ml"] / ML_PER_US_FL_OZ
df["uk_fl_oz"] = df["ml"] / ML_PER_UK_FL_OZ
df["diff_pct"] = (df["uk_fl_oz"] - df["us_fl_oz"]) / df["us_fl_oz"] * 100
# Roundtrip sanity check — US direction
df["ml_back_us"] = df["us_fl_oz"] * ML_PER_US_FL_OZ
assert (df["ml"] - df["ml_back_us"]).abs().max() < 1e-10, "roundtrip drift"
print(df.round(3))
# ml us_fl_oz uk_fl_oz diff_pct ml_back_us
# 0 30 1.014 1.056 4.084 30.0
# 1 100 3.381 3.520 4.084 100.0
# 2 250 8.454 8.799 4.084 250.0
# 3 500 16.907 17.598 4.084 500.0
# 4 750 25.361 26.396 4.084 750.0
# 5 1000 33.814 35.195 4.084 1000.0The diff_pct column is always 4.084%. That is the fixed ratio (29.5735 − 28.4131) / 28.4131, which is what the 1824 split locked in. If your data ever shows a different percentage, check which factor you actually used.
FAQ
How many ml is 1 fl oz exactly?
1 US fl oz = 29.5735 mL (NIST exact); 1 UK fl oz = 28.4131 mL (BIPM exact). The FDA also permits 1 fl oz = 30 mL on nutrition labels (21 CFR 101.9), which adds a 1.4% error. Use the precise factor for pharmacy, chemistry, customs and fill-volume audits; use 30 mL for everyday consumer reading.
What is 500 ml in fl oz?
500 mL = 16.907 US fl oz or 17.598 UK fl oz, a gap of about 0.69 fl oz (4%). A 500 mL bottle is labeled 16.9 fl oz in the US, 17.6 fl oz in the UK, and simply 500 ml under EU rules. Mental shortcut: 500 ÷ 30 ≈ 17 fl oz.
Is 30 ml equal to 1 fl oz?
Not exactly. 1 US fl oz = 29.5735 mL and 1 UK fl oz = 28.4131 mL. The 30 mL figure is an FDA-permitted rounding for nutrition labels, off by 1.4% from the US value and 5.6% from the UK value. Fine at the shelf, wrong at the pharmacy bench.
Why are US and UK fluid ounces different?
The 1824 Weights and Measures Act redefined the Imperial gallon as 277.42 cubic inches while the US kept the older Queen Anne gallon at 231 cubic inches. The US gallon splits into 128 fl oz, the Imperial gallon into 160, so the UK fluid ounce ended up 3.9% smaller even though the UK gallon is 20% larger.
How many ml in 8 oz of water?
Converting 8 oz in ml depends on whether “oz” means weight or volume. 8 US fl oz of water = 236.59 mL. Water sits near 1 g/mL, so the same 8 fl oz also weighs about 236 g = 8.35 oz by weight, close but not equal. For non-water liquids (honey, oil, syrup) the two “8 oz” numbers diverge by up to 40%. For reference, 16 US fl oz = 473.18 mL (the US pint boundary), a common query for Japanese recipe readers searching 16オンスは何ml.
How do I convert ml to fl oz in my head?
Divide mL by 30 for a 1.4% US approximation. 500 ÷ 30 ≈ 17 fl oz (exact 16.91). For UK recipes, divide by 28.4 instead. Precise work calls for mL ÷ 29.5735 (US) or mL ÷ 28.4131 (UK), or the volume converter. Alternatively, multiply by 0.033814 (US) or 0.035195 (UK) for the same result.
What is 100 ml in US fl oz?
100 mL = 3.381 US fl oz (precisely 3.3814). This is the number behind TSA’s 3-1-1 rule for carry-on liquids: the international cabin limit is 100 mL, rounded to 3.4 fl oz on US security signage. A bottle marked 3.5 fl oz exceeds 100 mL and will be confiscated.
Is a fluid ounce the same as an ounce for cooking?
Only for water, and only approximately. Water is the one liquid where 1 fl oz ≈ 1 oz by weight because its density sits near 1 g/mL. For honey (density 1.42) 8 fl oz weighs 11.85 oz; for flour (bulk density 0.55) 8 fl oz weighs 4.59 oz. Serious bakers weigh in grams and skip volume entirely.
Which countries use US fl oz and which use UK fl oz?
US fluid ounce: the United States, Liberia and Myanmar. Imperial fluid ounce: the UK (pub pints and some beverage contexts), Ireland, and legacy use in Canada, Australia, New Zealand, South Africa, India and Malaysia. The EU, China, Japan, Korea and most of the rest of the world label exclusively in mL and L.
How do I convert fl oz to ml?
Multiply US fl oz by 29.5735 or UK fl oz by 28.4131. For quick mental math in cooking, the FDA-approved shortcut of 30 ml per fl oz is within 1.4%. Use 29.5735 for pharmaceutical formulations and 28.4131 for UK recipes.