Tools /Diet

Weight & Volume Converter for Diabetes-Friendly Cooking

Convert between cups, grams, ounces, mL, lb, and kg. Plus why portion accuracy matters for blood sugar and which units to trust for carb counting.

3.5k shares·Updated May 14, 2026·Reviewed by clinician

Weight & volume converter

Everyday kitchen units

Value

From

Result

2.205 lb

From 1 kg

Medical disclaimer

Diabic articles are clinician-reviewed and sourced to peer-reviewed evidence, but they are educational, not personalised medical advice. Talk to your endocrinologist or primary-care provider before changing medication, insulin doses, or treatment. Learn more

A recipe calls for "1 cup of oats" but you need the exact carb count. Another recipe from an Australian food blog lists "1 cup flour" and you're cooking in a US kitchen. In both cases, the cups-to-grams conversion is not straightforward, and for someone managing blood sugar, getting it wrong can shift a carb estimate by 20 to 30 grams. This weight converter handles lb, kg, oz, g, cups, mL, fl oz, teaspoons, and tablespoons, and the guide below explains which units to trust for accurate carb counting.

How to use the weight and volume converter

Select your starting unit. Choose from weight units (pounds, ounces, kilograms, grams, stones) or volume units (US cups, metric cups, UK cups, fluid ounces, tablespoons, teaspoons, milliliters, liters).
Enter the amount. Type the number from your recipe, nutrition label, or clinic notes into the input field.
Select your target unit. The converter will display all equivalents simultaneously so you can see the full picture at once.
Use the gram or mL result for carb counting. For solid foods, the gram value from your kitchen scale is the most reliable input for a carb estimate. For liquids, the mL value matches what clinical fluid tracking uses.

The conversion constants

The values below are used verbatim in this tool's calculations. Weight constants come from NIST Handbook 44, which defines the legal tolerances for all US commercial weighing and measuring devices. Volume constants for US labeling use the FDA's reference amount of 240 mL per cup, as defined in 21 CFR 101.12. Metric and imperial constants follow ISO 80000-3 definitions for SI-derived units.

WEIGHT
1 pound (lb)        = 0.45359237 kilograms (kg)   [exact, NIST]
1 ounce (oz)        = 28.349523125 grams (g)      [exact, NIST]
1 stone (UK)        = 6.35029318 kg               [exact]
1 kilogram (kg)     = 2.20462262 lb               [reciprocal]

VOLUME
1 US cup            = 240 mL                      [US legal / FDA labeling]
1 US fluid ounce    = 29.5735296 mL               [US Customary]
1 UK (imperial) cup = 284.131 mL
1 imperial fl oz    = 28.4131 mL
1 US teaspoon       = 4.92892 mL
1 US tablespoon     = 14.7868 mL
1 metric cup        = 250 mL                      [Australia, some Europe]

NIST is the authoritative US source for all measurement standards, and its published conversion factors are the ones laboratories, pharmacies, and food manufacturers use. ISO (the International Organization for Standardization) harmonizes these definitions globally for SI units such as milliliters and grams. Using published constants rather than rounded approximations keeps carb estimates consistent across sessions.

Quick conversion charts

Weight conversions

Volume conversions

Why this matters for blood sugar

Portion size accuracy is a direct clinical lever for blood sugar management. Research on carbohydrate counting shows that visual estimates of food portions can vary by up to 50% compared to weighed amounts. For someone counting carbs, a 50% error in a cup of cooked rice (roughly 45 grams of carbohydrate per cup) could represent a 20+ gram swing in total carbs at a single meal. The American Diabetes Association Standards of Care identifies carbohydrate counting as an effective nutrition strategy for glycemic management, and its accuracy depends entirely on starting with reliable portion data.

Weight in grams is consistently more accurate than volume in cups for solid and semi-solid foods. This is not a minor technical detail. A measuring cup filled with rolled oats can vary by 15 to 25% depending on how firmly the oats are packed. The gram weight on a Nutrition Facts label reflects a standardized serving that was actually weighed, not scooped. Using a kitchen scale and matching its gram readout to the per-100-gram figures in USDA FoodData Central gives a carb estimate that is reproducible from one meal to the next.

The difference between a US cup and a metric cup is 10 mL, which sounds trivial until you apply it to flour. A US cup of all-purpose flour weighs approximately 120 to 125 grams. An Australian metric cup of the same flour weighs closer to 130 to 135 grams because the cup holds 250 mL rather than 240 mL. A UK cup holds 284 mL and would give even more flour by weight. Over a full baking recipe with multiple cups of flour and sugar, these discrepancies compound. People with diabetes who follow international food blogs need to convert correctly or their carb estimates drift systematically in one direction.

Fluid intake tracking becomes critical during sick days, high blood sugar episodes, and any situation where dehydration could worsen hyperglycemia or increase DKA risk. Hospital discharge instructions and clinical fluid goals are always stated in milliliters, not "glasses" or "cups." Knowing that a standard hospital cup is 240 mL (matching the US labeling standard) and that a tall diner glass may hold 400 to 480 mL helps translate clinical guidance into real-world behaviour. Separately, pharmacy syringes and oral medication measuring devices are calibrated in mL. Insulin pen cartridges hold 3 mL, which equals 300 units of U-100 insulin. Developing comfort with mL as a unit reinforces safer medication and fluid literacy.

A worked example

Mei was diagnosed with Type 2 diabetes two years ago and has become careful about tracking carbohydrates. She follows an Australian baking blog and finds a recipe for whole-wheat banana muffins. The recipe lists "1 cup wholemeal flour" and the blogger notes this equals 150 grams.

Mei reaches for her US measuring cup and fills it with flour. She assumes a cup is a cup. The problem is that her US cup holds 240 mL, while the Australian blogger's metric cup holds 250 mL. More critically, the blogger likely spooned the flour lightly into the cup and levelled it off, arriving at 150 grams for 250 mL. Mei's US cup, filled the same way, holds approximately 120 to 125 grams of the same flour.

That discrepancy, 150 grams versus 125 grams, represents roughly 18 grams of carbohydrate difference per cup of flour across a six-muffin batch. If Mei counts 25 grams of carbs per muffin based on the recipe as written but her muffins actually contain 22 grams, the error is manageable. But if she scales the recipe, uses different flour, or makes the same kind of assumption with oats and brown sugar in the same recipe, the errors stack.

The practical takeaway is simple: when a recipe gives both a volume measure and a gram weight, use the gram weight and a kitchen scale. If you only have a volume measure from an international recipe, use this converter to check whether the cup definition matches yours before estimating carbs. Gram-based carb counting is reproducible; cup-based carb counting is an approximation.

When to trust grams over cups

Rice (cooked and uncooked), oats, and most grains. These pack unpredictably in a measuring cup. A "cup" of dry rolled oats ranges from 80 grams (lightly spooned) to 110 grams (packed). The gram weight removes that ambiguity.
Flour of all types. Volume measures of flour are notoriously variable. Professional bakers weigh flour for consistency, and people counting carbs should do the same.
Nut butters, hummus, and other thick spreads. A tablespoon of peanut butter heaped versus levelled can differ by 30 to 40%. Gram weights reflect what's actually eaten.
Granola and cereal. Serving sizes on these labels are almost always given in grams for this reason. A cup of granola varies dramatically by brand density and particle size.
Liquids (water, milk, broth, juice). Volume measures work well here because liquids are incompressible and fill a cup consistently. A US cup of water is reliably close to 240 mL (and 240 grams, since water's density is 1 g/mL). Volume is fine for these.
When you only have a volume measure. Use this converter to get the mL value, then look up the food in USDA FoodData Central by its per-100-mL carb content for liquids, or accept the volume estimate with the understanding that it carries more uncertainty than a weighed amount.

Calorie Calculator for estimating daily energy needs based on weight, height, and activity.
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Sources

National Institute of Standards and Technology. NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. https://www.nist.gov/pml/owm/publications/handbook-44
US Food and Drug Administration. Reference Amounts Customarily Consumed Per Eating Occasion (21 CFR 101.12). Defines the US cup as 240 mL for nutrition labeling purposes.
American Diabetes Association. Standards of Care in Diabetes: Nutrition Therapy. Diabetes Care. 2026;49(Supplement 1). https://diabetesjournals.org/care/issue/47/Supplement_1
Evert AB, Dennison M, Gardner CD, et al. Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report. Diabetes Care. 2019;42(5):731-754. https://doi.org/10.2337/dci19-0014
USDA Agricultural Research Service. FoodData Central. https://fdc.nal.usda.gov/

FAQ

Questions about the Weight & Volume Converter for Diabetes-Friendly Cooking

A US cup holds 240 mL by the FDA labeling standard, but the weight in grams depends entirely on what you're measuring. Water weighs 240 grams per US cup. All-purpose flour weighs roughly 120 to 130 grams per US cup depending on how it's measured. Cooked rice weighs approximately 175 to 200 grams per cup. There is no single answer because density varies by food. For carb counting, always look for a gram weight rather than relying on a volume-to-gram conversion without knowing the food's density.

No. A US cup used for nutrition labeling is defined as 240 mL. A UK (imperial) cup is 284.13 mL. An Australian metric cup is 250 mL. The difference between a US cup and a UK cup is about 18%, which is large enough to affect carb estimates in recipes with multiple cup measures. When following a recipe from a British or Australian source, check which cup definition the recipe author used, and convert accordingly using the charts above.

Measuring cups measure volume (how much space something takes up). Kitchen scales measure mass (how much matter is actually there). For any food that is not pure liquid, volume and mass have a non-linear relationship governed by density and packing. Rice grains, oat flakes, and flour particles trap air between them, so the same cup volume can hold very different gram amounts depending on how the food was poured, scooped, or shaken. The scale gives you the actual mass, which is what the Nutrition Facts label's gram-based serving sizes refer to.

For solid and semi-solid foods, gram weight from a kitchen scale is more accurate. Nutrition Facts labels list carbohydrate content per gram of food, so weighing your portion and comparing it to the per-100-gram figures in the label or in USDA FoodData Central gives a reliable carb estimate. Volume (cups, tablespoons) introduces packing variability that does not exist when you weigh. For liquid foods like juice, milk, or broth, volume measures in mL are accurate enough because liquids are consistent in density. The Evert et al. consensus report in Diabetes Care supports gram-based carb counting as the most precise method available outside of clinical settings.

In the US, FDA regulations allow a 20% variance on most nutrient declarations, meaning a label that says 30 grams of carbohydrate per serving could legally reflect anywhere from 24 to 36 grams. For people with diabetes managing postprandial glucose tightly, this inherent variance is worth knowing. Gram-based weighing reduces one source of error (the portion size), even though label rounding introduces a separate one. Using consistent brands and cross-checking against USDA FoodData Central data can help narrow uncertainty further.

A US fluid ounce equals 29.5735 mL. A UK (imperial) fluid ounce equals 28.4131 mL. The two are close but not identical, and the distinction matters when converting medication volumes or international beverage recipes. Pharmacy syringes and clinical fluid measurements always use mL, so when a discharge summary or sick-day plan refers to fluid targets, the mL column in this converter is your reference.

The traditional US customary cup is defined as 8 US fluid ounces, which equals exactly 236.588 mL. The FDA's legal definition for nutrition labeling rounds this to 240 mL for simplicity. Most US measuring cups are manufactured to the 240 mL labeling standard. The 3.4 mL difference is less than 1.5% and is unlikely to affect carb counts meaningfully in practice. This converter uses 240 mL, the FDA labeling standard, as the definition of a US cup.

Written by

Shahriar P. Shuvo

Author and Founder at Diabic

Shahriar P. Shuvo is the founder of Diabic. He has lived with diabetes for over 14 years, and built Diabic to deliver the practical, evidence-based self-management tools he wished existed when he was first diagnosed. By trade, Shahriar is a senior design and frontend engineer with 6+ years shipping products at Agora, Timescale (now Tiger Data), and ShareTrip. He writes from the intersection of lived diabetes experience and product craft, focused on what works in daily management rather than what sounds good in a textbook.

Medically reviewed by

Dr. Rezwana Rumpa

MBBS, MRCOG(UK), MRCPI(IE)

BMDCA68043

Dr. Rezwana Parvin Rumpa is an obstetrics and gynaecology specialist with clinical focus on gestational diabetes, PCOS, and fertility. She holds the MRCOG (Final Part) from the Royal College of Obstetricians and Gynaecologists in London, the MRCPI (Final Part) from the Royal College of Physicians of Ireland, and an MBBS from Shaheed Monsur Ali Medical College under Dhaka University. Dr. Rumpa serves as a Senior Medical Officer in the Obs and Gynae department at BRB Hospitals Ltd, where she has spent three years managing prenatal care, emergency obstetric cases, and women's-health surgery. On Diabic, she medically reviews content for women living with diabetes, with particular attention to pregnancy, PCOS, and reproductive-health intersections.

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