How Many Grams in an Ounce? 28.35 g (Plus Troy Ounce)
A butter recipe and a gold coin both use the word ounce, but the two units do not weigh the same: a standard ounce is exactly 28.349523125 grams according to NIST (US federal measurement authority), while a troy ounce comes to 31.1034768 grams. The sections below sort out which ounce is meant, what the gram figure looks like for everyday weights, and where rounding changes the answer.
Avoirdupois ounce in grams: 28.35 g (exact 28.349523125 g) · Troy ounce in grams: 31.10 g (exact 31.1034768 g) · Ounces in one pound: 16 · Half an ounce in grams: 14.1748 g
Quick snapshot
- One avoirdupois ounce equals exactly 28.349523125 g (Convertitive (conversion guide site))
- One troy ounce equals exactly 31.1034768 g (NIST (US federal measurement authority))
- One ounce is one sixteenth of a pound (Royal Mint (UK national mint))
- Rounding one ounce to 28 g undercounts by about 1.23%, according to USCalc (online calculator site)
- The research did not include a primary government record of the 1959 pound agreement, so that date rests on secondary summaries. (USCalc (online calculator site))
- The 1959 international agreement fixed the pound at exactly 0.45359237 kg, according to OZtoGram (unit converter site)
- Precious metals were weighed in troy units during the Middle Ages, per Royal Mint (UK national mint) (OZtoGram (unit converter site))
- The name troy traces to the French city of Troyes, according to Investopedia (financial reference publisher)
- Food labels and postage keep the avoirdupois ounce, while the troy ounce stays with precious metals, according to Money Metals (bullion dealer)
- The London Bullion Market Association reportedly requires bar weights in multiples of 0.025 troy ounce, according to Arteon (unit converter site)
Six figures, one pattern: the troy ounce outweighs the avoirdupois ounce by about 2.75 grams, according to Royal Mint (UK national mint), so a conversion that works on a shopping list can fail on a metal invoice.
| Measure | Value |
|---|---|
| Avoirdupois ounce in grams | 28.35 g (exact 28.349523125 g), Convertitive (conversion guide site) |
| Grains per avoirdupois ounce | 437.5, Money Metals (bullion dealer) |
| Grains per troy ounce | 480, Money Metals (bullion dealer) |
| US fluid ounce in milliliters (volume, not mass) | 29.5735295625 mL, Xerobit (conversion tool site) |
| Troy pound in grams | 373.2417 g, Gold Calculator Hub (gold weight calculator) |
| Troy ounces per troy pound | 12, Gold Calculator Hub (gold weight calculator) |
How many grams is exactly 1 oz?
The avoirdupois ounce defined
- One avoirdupois ounce equals exactly 28.349523125 grams (NIST (US federal measurement authority)).
- Avoirdupois is the everyday system for general weights, while the troy ounce is kept for metals.
Rounded value for everyday use
- Rounded to two decimals, one ounce is 28.35 grams (CalcWisp (online calculator site)).
- US nutrition labels reportedly use a rounded 28 g per ounce, according to CalcWisp (online calculator site).
- Quick mental math multiplies ounces by 28; for 4 oz that gives 112 g against an exact 113.4 g, according to IFCalculator (unit conversion site).
Conversion formula
- Grams equal ounces multiplied by 28.349523125, and the same factor applies to any quantity.
- Round the product only at the end, so that small rounding steps do not stack up across a calculation.
The implication: for a kitchen scale or a shipping label, 28.35 is the working number, and the exact factor matters only when a document asks for milligram precision.
How many grams are in 8 ounces?
Calculation for 8 ounces
- The factor of 28.349523125 g per ounce, as used by Xerobit (conversion tool site), gives about 226.80 g for 8 oz and 113.40 g for 4 oz.
- Multiply the number of ounces by 28.349523125.
- Keep the full product unrounded until the last step, so the rounding happens once.
- Round to two decimals for everyday use, so 8 oz becomes 226.80 g.
Why 8 oz is not 250 g
- 250 minus 226.80 leaves 23.20 g, so 8 oz is about 23 grams lighter than a 250 g pack.
- Rounding one ounce to 28 g undercounts by about 1.23%, according to USCalc (online calculator site).
A cook can live with a 28 g shortcut on a shopping list. A metals trader cannot, because the same shortcut applied to a troy order is a different unit altogether.
The implication: an 8 oz pack and a 250 g pack are not interchangeable, so a shopper comparing unit prices should convert both to the same unit first.
What is a troy?
Troy ounce weight
- A troy ounce equals exactly 31.1034768 grams, according to OZtoGram (unit converter site).
- The troy-to-avoirdupois ratio is about 1.09714, which makes the troy ounce about 9.7% heavier, per Lone Star Coins (coin dealer).
Where troy ounces are used
- Gold, silver, platinum and palladium are quoted per troy ounce on major commodity exchanges, according to Lone Star Coins (coin dealer).
- A troy ounce of 14K gold weighs 31.1 g but contains only 18.14 g of pure gold, per Gold Calculator Hub (gold weight calculator).
Using the wrong ounce type gives an incorrect valuation for precious metals, according to Xerobit (conversion tool site). A buyer should confirm the unit on the invoice before comparing prices.
The implication: a price per gram means nothing until the buyer confirms which ounce sits behind the quote.
What is heavier, 1 ounce or 1 gram?
Size comparison
- One ounce (28.35 g) is heavier than one gram, and it is about 28 times the weight of one gram, per IFCalculator (unit conversion site).
- A standard 14-ounce can weighs 396.89 grams, roughly 400 one-gram weights, according to Arteon (unit converter site).
Ratio of ounce to gram
- The ounce-to-gram ratio is about 28.35 to 1, which is why a gram scale reads in much finer steps than an ounce scale (CalcWisp (online calculator site)).
- A cook measuring small amounts gains precision by reading in grams instead of rounding to the nearest ounce.
The implication: an ounce is a coarse unit for small amounts, so a recipe that mixes the two needs converting, not guessing.
Is 14 grams one ounce?
Gram value in ounces
- 14 grams equals about 0.49 ounces, and it sits just below the half-ounce mark of 14.1748 grams, per Convertitive (conversion guide site).
Why 14 g is close to half an ounce
- 14 grams is not one ounce. One ounce is 28.35 grams, so 14 grams is about half of it, per IFCalculator (unit conversion site).
- For most cooking the near match is close enough, but on a postal or lab scale the gap is real.
The catch: 14 grams is a near miss, not a match, so any recipe or invoice that treats it as one ounce is off by about half.
Three units, one pattern: the troy ounce is the heaviest of the three, so the same number on a label means a different weight depending on which ounce the writer meant, as Investopedia (financial reference publisher) explains when it traces the troy system to the Middle Ages.
| Unit | Grams per unit | Where it is used |
|---|---|---|
| Avoirdupois ounce | 28.349523125 g | Food labels and postage |
| Troy ounce | 31.1034768 g | Gold, silver, platinum and palladium |
| Gram | 1 g | Metric base unit for small weights |
Confirmed facts
- One avoirdupois ounce is exactly 28.349523125 grams, per NIST’s conversion sheet.
- One troy ounce is exactly 31.1034768 grams, per NIST’s troy conversion sheet.
- One ounce is one sixteenth of a pound, per the Royal Mint.
- Half an ounce is 14.1748 grams, half of the NIST avoirdupois factor.
What’s unclear
- Whether rounding to 28.35 g suits a given purpose; the research offers no rule for that.
- The 1959 date rests on secondary summaries, because no primary government record was in the research.
- Regional usage in the UK and US: the research gives only general statements.
- The London Bullion Market Association bar-weight rule rests on a single aggregator, not an official rulebook.
Verdict: A recipe writer or invoice clerk who treats 14 grams as one ounce gets a weight about half the true figure, so the unit on the page has to match the scale or the quote.
The troy ounce takes its name from the French city of Troyes, and precious metals were weighed in troy units during the Middle Ages.
— Investopedia (financial reference publisher)
The 1959 international yard and pound agreement fixed the pound at exactly 0.45359237 kg.
— OZtoGram (unit converter site)
For a home cook, a parcel sender or a bullion buyer, the choice is clear: convert with the everyday ounce for food and post, and check for the word troy before pricing any gold or silver, or the wrong ounce quietly sets the wrong weight.
Related reading: 1/2 cup in grams conversion guide
Related reading: 1/2 cup in grams conversion guide
Frequently asked questions
Is 8 oz the same as 250g?
No. Eight ounces is about 226.80 g, roughly 23 g less than 250 g.
Is 100g the same as 4 oz?
No. 100 g is about 3.53 oz, while 4 oz is about 113.40 g, so 4 oz is the heavier figure.
Is 12g half an ounce?
No. 12 g is about 0.42 oz, while half an ounce is 14.1748 g.
How many grams are in half an ounce?
Half an ounce is 14.1748 grams, calculated from the exact avoirdupois factor of 28.349523125 g per ounce.
How do I convert grams back to ounces?
Divide the gram figure by 28.349523125. For example, 28.35 g works out to one avoirdupois ounce.
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