How to Calculate Gold Value by Weight and Karat
Gold value depends on weight, purity, and the spot price basis. Equal weight does not mean equal value if the karat is different.
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Quick answer
Estimate gross gold-content value by converting the gold-bearing weight to the price unit, applying the selected purity or fineness, and multiplying by the gold price you enter. Calzivo does not fetch a live price, test purity, or predict a buyer offer.
Use the calculators: Use the Gold Calculator for gross metal-content value or the Scrap Gold Calculator for gross melt value and an optional user-entered payout scenario.
The calculation path
This is the traditional educational karat ratio. The calculators use the exact displayed marked-fineness preset or custom fineness.
Do not round purity or converted weight before the final displayed result.
Convert either weight or price basis first when the units differ.
Units must match
- One troy ounce equals 31.1034768 g in the calculator helper.
- One ordinary avoirdupois ounce equals 28.349523125 g and is not interchangeable with a troy ounce.
- One pennyweight equals 1.55517384 g, and 20 pennyweight equals one troy ounce.
- Gold price can be entered per gram or per troy ounce; weight can be grams, kilograms, troy ounces, ordinary ounces, or pennyweight.
- The selected currency code labels the result only and does not convert exchange rates.
Formula substitutions and worked examples
For 10 g at 18K and an entered pure-gold price of 70 per gram: purity = 18 / 24 = 0.75; pure-gold weight = 7.5 g; gross metal-content value = 7.5 x 70 = 525.
For 20 g at the theoretical 14 / 24 ratio and 65 per gram: pure-gold weight = 20 x 14 / 24 = 11.666666... g; value = approximately 758.33. Do not first round purity to 0.58. The calculator 14K (585) preset instead uses 58.5% and produces 760.50 under the same weight and entered price.
One troy ounce is 31.1034768 g, while one ordinary ounce is 28.349523125 g. At the same fineness and per-gram price, the troy-ounce input represents about 2.753953675 g more material. Select the intended unit; the calculator does not infer it.
For 10 g of 18K and 10 g of 14K, calculate each lot separately. The theoretical ratios give 7.5 g plus 5.833333... g = 13.333333... g pure-gold equivalent. The calculators are single-item tools, so run each lot separately and sum only comparable results.
If gross melt value is 525 and the user chooses a 90% payout scenario, estimated payout = 525 x 0.90 = 472.50. That percentage is an assumption, not a guaranteed offer or a model of specific fees.
Calculator presets and actual composition
The calculators use displayed presets 999, 916, 750, 585, and 417 parts per thousand. These common marked-fineness values are not identical to every theoretical karat ratio. A hallmark or stamp does not let Calzivo verify composition; testing may be appropriate when authenticity or payable content matters.
Assumptions and limitations
- Enter only estimated gold-bearing solid-material weight and exclude stones and clearly non-gold components where possible.
- Plated, filled, rolled-gold, vermeil, soldered, or mixed-material items cannot be valued reliably from total item weight.
- Market prices can change rapidly, and the calculator uses only the price entered by the user.
- Gross metal-content value excludes craftsmanship, collectible value, taxes, shipping, refining, assay, buyer margin, and transaction costs.
- Results do not establish authenticity, legal title, tax treatment, appraisal value, or a guaranteed sale value.
- Professional assay or transaction verification may be appropriate; results are educational, not financial, investment, tax, legal, appraisal, or selling advice.
Frequently asked questions
Does Calzivo fetch the current gold price?
No. Enter your own price and choose whether it is per gram or per troy ounce.
Should I use a troy ounce or an ordinary ounce?
Use the unit that matches your measurement. They are different: one troy ounce is 31.1034768 g and one ordinary ounce is 28.349523125 g.
Why can the calculator preset differ from karat divided by 24?
The calculator applies its displayed marked-fineness preset. For example, 14K uses 585 parts per thousand rather than the theoretical repeating ratio 14 / 24.
Can I combine mixed-karat items in one entry?
No. Run each weight-and-fineness lot separately, then sum results that use the same currency and price basis.
Is gross metal-content value a buyer offer?
No. It excludes testing, recoverable weight, refining, commercial margin, transaction costs, and buyer policy.
Reference check
Sources and references
These references provide background context for the topic. They do not replace professional advice or official documents.
- Buying Platinum, Gold, and Silver Jewelry
Federal Trade Commission
- Jewelry, Precious Metals, and Pewter Industries
Federal Trade Commission
- Precious Metals Conversion Information
National Institute of Standards and Technology
- Conversion Factors for Precious Metal Sales
National Institute of Standards and Technology
- Hallmarking: Practical Guidance
British Hallmarking Council
- Hallmarking: Fineness Guidance
British Hallmarking Council
- Methods for Determining Gold Content of Jewelry Metals
Gemological Institute of America
- LBMA Precious Metal Prices
London Bullion Market Association
Gold value is based on pure gold content, so weight, karat, and spot price all matter.
Use the tool instead
Use the matching calculator when you want to plug in your own numbers and get a result faster.
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