Pennyweights to Grams Converter

What this converter does

It converts pennyweights to grams by multiplying by exactly 1.55517384. The pennyweight is a twentieth of a troy ounce and the everyday working unit of North American jewellers and scrap-gold buyers, which makes this one of the more practically useful conversions in the cluster despite the unit being unknown outside that trade.

The formula

Multiply pennyweights by exactly 1.55517384. The constant is the troy ounce of 31.1034768 grams divided by 20, so it is exact and derives ultimately from the grain. A pennyweight is also exactly 24 grains, which ties it to the same foundation the avoirdupois system rests on.

Worked examples

One pennyweight is 1.555 g. Ten pennyweights is 15.552 g. Twenty pennyweights is 31.103 g, which is exactly one troy ounce. A typical gold ring at 5 g is 3.215 dwt, and a scrap lot of 200 dwt is 311.03 g, or ten troy ounces.

Where the name comes from

From the mass of an English silver penny in the medieval period, when coinage weight and unit weight were the same thing. The coin changed and eventually disappeared; the unit outlived it and remains in daily use in North American jewellery, where quantities at the scale of a ring or a chain land in convenient whole numbers. The abbreviation dwt combines the d of denarius, the Roman coin behind the penny, with the wt of weight — a small piece of etymology that explains an otherwise baffling abbreviation.

Why scrap buyers use it

Because it fits the quantities. A piece of jewellery weighs a few pennyweights, a day of buying runs to a few hundred, and prices can be quoted per pennyweight as a simple number without anyone dividing an ounce price mentally. There is nothing improper about the convention — it is a working unit sized to the work — but it does mean that comparing a per-pennyweight offer with a per-gram offer requires converting one into the other first, since the pennyweight figure will always look larger simply because the unit is larger.

Converting prices as well as weights

To compare offers, divide a price per pennyweight by 1.55517384 to get the equivalent per gram, or multiply a per-gram price by the same figure to go the other way. The mass conversion and the price conversion use the same constant in opposite directions, which is the standard relationship for any per-unit price. Doing the mass first and the money second keeps the direction visible, since the smaller unit always carries the smaller price.

Purity is a separate question

Mass conversion is indifferent to karat: 10 dwt of 14-karat gold and 10 dwt of 24-karat gold are both 15.552 g. What differs is fine content — the 14-karat piece is 14 parts in 24 gold, so 9.07 g of fine metal against 15.55 g for the pure piece. A scrap offer should state whether it is priced on gross weight or on fine content, and the difference between those two bases is far larger than any spread between competing buyers. This page converts the mass; the fineness step belongs to the transaction.

The troy chain in full

Twenty-four grains make a pennyweight, twenty pennyweights make a troy ounce, and twelve troy ounces make a troy pound. Every step is exact, so a pennyweight figure can be pushed in either direction without accumulating error: multiply by 24 for grains, divide by 20 for troy ounces. Those two operations cover almost everything a jeweller needs, and the gram conversion on this page connects the whole chain to metric equipment.

Common mistakes

Comparing a per-pennyweight price directly against a per-gram price without converting. Confusing the pennyweight with the avoirdupois ounce, which is eighteen times larger. Ignoring fineness when valuing scrap. And assuming the unit is used everywhere — European and Asian dealers work in grams, so a pennyweight figure is specifically a North American convention and needs converting for anyone else.

Benchmarks

1 dwt is 1.555 g. 2 dwt is 3.110 g. 5 dwt is 7.776 g. 10 dwt is 15.552 g. 20 dwt is 31.103 g, one troy ounce. 50 dwt is 77.759 g. 100 dwt is 155.517 g. 240 dwt is 373.242 g, one troy pound. The twenty-to-the-ounce relationship is the one to hold, since it connects the working unit to the pricing unit in one step.

Accuracy and limits

Exact factor, exact decimal arithmetic, display-only rounding, and refusal of ambiguous input with an explanation. The tool converts mass. Purity, fine content, refining charges and the basis on which an offer is made are all outside what a unit conversion can address, and this page names them rather than implying the mass figure settles the value.

Weighing a mixed lot

Scrap arrives as a mixture of karats, and a single gross weight cannot yield a fine content without knowing the split. The practical procedure is to sort by karat stamp, weigh each group separately, convert each, and apply that group fineness. A lot weighed as one figure and valued at an average assumed karat is being valued on a guess, and the guess is usually not in the seller favour. Sorting takes minutes and is the highest-value step in the whole transaction.

What the stamp does and does not tell you

A karat stamp is a manufacturer claim, and reputable pieces meet it. Unstamped, worn or misrepresented pieces exist, which is why buyers test rather than trust — acid testing, electronic testing or, for larger lots, assay. The mass conversion on this page is exact regardless; what testing establishes is how much of that mass is gold, which is the other half of any valuation and the half no converter can supply.

Refining charges

A buyer offer reflects the refining cost between the scrap and the saleable metal, which is why an offer sits below the spot value of the fine content. That gap is a legitimate cost rather than a markdown, and it varies with lot size — small lots carry proportionally more of it. Understanding that the difference between the converted mass value and the offer is mostly refining economics, rather than a units problem, keeps the negotiation focused on the right variable.