---
title: "Understanding Gold Weight Units: Grams, Troy Ounces, and More"
source: "https://goldealers.co.uk/knowledge/gold/gold-weight-units-explained"
date: "2025-12-02"
---

# Understanding Gold Weight Units: Grams, Troy Ounces, and More

Precious metals are measured differently than everyday items, which can confuse sellers. This article clarifies the various weight units used for gold – particularly the troy ounce versus regular ounce distinction – and provides practical conversion tools. Understanding these measurements helps you accurately estimate your gold's value and verify dealer quotes.

> **Quick Summary:** A troy ounce is a special unit of weight used for precious metals. It equals approximately 31.1 grams. It's different from the everyday ounce (avoirdupois ounce) which is about 28.35 grams. Historically, the troy ounce has been the standard for gold, silver, platinum, etc., which is why market prices are quoted per troy ounce. For example, if gold is £1,500 per troy ounce, that means about £48.23 per gram. Understanding this helps when you convert between the weight of your items and the market price.

## The Troy Ounce Explained

Understanding why precious metals use a different measurement system.

### What Is a Troy Ounce?

**Definition and Origin:**

**Basic Facts:**
- 1 troy ounce = 31.1034768 grams (usually rounded to 31.1g)
- Symbol: "oz t" or "ozt"
- Named after Troyes, France (medieval trading city)
- Used since at least the 16th century
- International standard for precious metals

**Historical Context:**
- Derived from Roman monetary system
- Standardised for European trade
- Adopted globally for consistency
- Still used despite metric system
- Prevents confusion in precious metals trade

**Why Troy Ounce Persists:**
- Universal understanding in bullion markets
- Historical continuity in contracts
- Legal tender coins specified in troy ounces
- Easier than constantly converting grams
- International gold/silver prices quoted in troy oz

> When you see gold prices quoted as "£1,500/oz" in financial news, that's per troy ounce, not regular ounce. This distinction is crucial for calculations.

### Troy Ounce vs Avoirdupois Ounce

**The Confusing Difference:**

**Avoirdupois Ounce (Regular Ounce):**
- 1 avoirdupois oz = 28.3495 grams
- Used for everyday items (food, postal weight, body weight)
- 16 oz = 1 pound (lb)
- What kitchen scales typically measure
- Abbreviated "oz" without the "t"

**Troy Ounce (Precious Metals):**
- 1 troy oz = 31.1035 grams
- Used exclusively for gold, silver, platinum, palladium
- 12 troy oz = 1 troy pound
- What precious metal scales measure
- Abbreviated "oz t" or "ozt"

**Key Difference:**
- Troy ounce is ~10% heavier than regular ounce
- 1 troy oz ≈ 1.097 avoirdupois oz
- Mixing them up causes significant errors
- Always confirm which type when reading scales

**Example of Confusion:**
- You weigh gold coin on kitchen scale: shows 1.1 oz
- That's 1.1 avoirdupois oz = 31.2g = ~1.003 troy oz
- If you assume 1.1 troy oz (34.2g), you'd overestimate value
- Always convert to grams first for accuracy

[How gold prices are calculated](/knowledge/gold/gold-prices-determined)

## Other Weight Units

Less common measurements you might encounter.

### Grams (Metric)

**The Universal Standard:**

**Why Grams Are Useful:**
- Metric system simplicity
- Easy decimal calculations
- Precise for small quantities
- Common in UK jewellery
- Goldealers typically quotes per gram

**Conversions:**
- 1 troy oz = 31.1035 grams
- 1 gram = 0.032151 troy oz
- Easy to scale (10g, 100g, 1000g)
- Most accurate for mixed lots

**Practical Usage:**
- Jewellery scales measure in grams
- Easier for customers to understand
- Simplifies percentage calculations (e.g., 18ct = 75% of gram weight)
- UK-friendly (familiar with grams from food packaging)

**Example:**
- Gold ring weighs 5.3 grams
- 18ct purity = 75% gold
- Pure gold content = 5.3g × 0.75 = 3.975g
- If gold = £48/g, value = 3.975g × £48 = £190.80

> Goldealers primarily works in grams for customer convenience. It's simpler for most UK sellers than troy ounces.

### Pennyweight (dwt)

**Historical Jewellers' Unit:**

**What It Is:**
- 1 pennyweight (dwt) = 1.55517 grams
- 20 pennyweights = 1 troy ounce
- Old British coin weight (silver penny)
- Still used by some US jewellers
- Rarely used in UK now

**Why You Might See It:**
- Antique jewellery documentation
- American estate jewellery
- Old appraisal certificates
- Jewellery trade jargon
- Some US dealer quotes

**Conversions:**
- 1 dwt = 1.555g = 0.05 troy oz
- 1 troy oz = 20 dwt
- 1 gram = 0.643 dwt

**Practical Note:**
- If you see pennyweight on old documents, convert to grams
- Not necessary to use in modern UK transactions
- Goldealers doesn't quote in dwt
- Interesting historical curiosity

### Grains (gr)

**Smallest Traditional Unit:**

**Definition:**
- 1 grain = 0.06479891 grams
- 480 grains = 1 troy ounce
- 24 grains = 1 pennyweight
- Based on weight of grain of wheat (historically)

**Where It's Used:**
- Ammunition/ballistics industry
- Pharmaceuticals
- Very rarely for gold except historical documents
- Sometimes dental gold weights

**Conversions:**
- 1 gram = 15.432 grains
- 1 troy oz = 480 grains
- Extremely fine measurement

**Practical Relevance:**
- You'll probably never need grains for selling gold
- Included for completeness
- If mentioned on very old documents

### Tael (Asian Markets)

**Regional Unit:**

**What It Is:**
- Traditional Chinese weight unit
- 1 tael ≈ 37.5 grams (Hong Kong tael)
- Varies by region (Singapore, Taiwan use different taels)
- Common in Asian gold markets
- Used for gold bars and jewellery

**Relevance to UK Sellers:**
- If you have Asian-origin gold bars
- Some marked in taels
- Convert to grams for UK sales
- Goldealers can handle tael-marked items

**Example:**
- 1 HK tael gold bar = 37.5g
- At £48/g = £1,800 value
- No need to use tael in calculation with Goldealers

> If your gold items have unusual weight markings (taels, baht, mace), just note them when selling. Goldealers will weigh items in grams/troy oz and value accordingly.

## Practical Conversions

Essential conversion formulas for everyday use.

### Quick Conversion Reference

**Most Common Conversions:**

**Troy Ounce ↔ Gram:**
- 1 troy oz = 31.1035g
- 1g = 0.032151 troy oz
- **Quick estimate:** 1 troy oz ≈ 31g

**Troy Ounce ↔ Avoirdupois Ounce:**
- 1 troy oz = 1.097 regular oz
- 1 regular oz = 0.911 troy oz
- **Remember:** Troy is ~10% heavier

**Common Bullion Weights:**
- 1 troy oz coin = 31.1g
- 1/2 troy oz = 15.55g
- 1/4 troy oz = 7.78g
- 1/10 troy oz = 3.11g

**Sovereign Weights:**
- Full Sovereign = 7.988g (0.2354 troy oz)
- Half Sovereign = 3.994g (0.1177 troy oz)
- Contains 7.322g pure gold (full) / 3.661g (half)

### Conversion Calculators

**How to Calculate:**

**From Troy Oz to Grams:**
- Multiply troy oz by 31.1035
- Example: 5 troy oz × 31.1035 = 155.52g

**From Grams to Troy Oz:**
- Divide grams by 31.1035
- Example: 100g ÷ 31.1035 = 3.215 troy oz

**From Price Per Troy Oz to Price Per Gram:**
- Divide troy oz price by 31.1035
- Example: £1,500/troy oz ÷ 31.1035 = £48.23/g

**From Price Per Gram to Price Per Troy Oz:**
- Multiply gram price by 31.1035
- Example: £50/g × 31.1035 = £1,555.18/troy oz

> **Memory Aid:** Remember "31" for troy ounce to grams. Close enough for quick estimates (actual: 31.1035).

### Online Tools

**Conversion Resources:**

**Recommended Calculators:**
- Goldealers website calculator
- Kitco weight converter
- BullionVault conversion tool
- Google (type "31.1g to troy oz" directly)
- Smartphone calculator apps

**Mobile Apps:**
- "Gold Calc" (iOS/Android)
- "Precious Metal Calculator"
- "Kitco Mobile" app
- Built-in calculator with formula

## Weighing Your Gold

Practical tips for accurate measurements.

### Home Weighing

**Using Kitchen or Postal Scales:**

**What You Need:**
- Digital scale (preferably 0.1g accuracy)
- Clean, flat surface
- Good lighting
- Small container/tray if weighing tiny items
- Note: kitchen scales usually measure avoirdupois oz

**Best Practices:**
- Calibrate scale if possible (use known weight)
- Tare (zero) with container before adding gold
- Weigh items individually first
- Then weigh total batch
- Record weights immediately

**Common Mistakes:**
- Forgetting to tare the container
- Assuming scale measures troy oz (usually doesn't)
- Weighing stones/non-gold parts
- Not calibrating scale
- Rounding too aggressively

**Accuracy Limitations:**
- Kitchen scales: ±1-2g accuracy typical
- Postal scales: ±5g sometimes
- Good enough for estimates
- Dealer will use professional scales for final weight

> Home scales give estimates only. Goldealers uses certified professional scales accurate to 0.01g for fair, precise valuations.

### Professional Scales

**What Dealers Use:**

**Jeweller's/Troy Scales:**
- Precision to 0.01g or better
- Often display grams and troy oz simultaneously
- Calibrated regularly
- Certified for trade
- Temperature compensated

**Goldealers' Equipment:**
- Professional jeweller's scales
- Regular calibration
- Multiple scales for cross-checking
- Certified accuracy
- Transparent weighing (customer can observe)

**Why It Matters:**
- Fair payments require precision
- Small differences significant on gold prices
- Legal requirement for trade
- Customer confidence
- Industry standard compliance

## Using Weight to Estimate Value

Applying weight knowledge practically.

### Simple Valuation Formula

**Basic Calculation:**

**Formula:**
```
Value = Weight (g) × Purity (%) × Gold Price (£/g)
```

**Example 1: Simple**
- Item weight: 10g
- Purity: 18ct (75% gold)
- Gold price: £48/g pure
- Pure gold content: 10g × 0.75 = 7.5g
- Value: 7.5g × £48 = £360 (before dealer margin)

**Example 2: Multiple Items**
- 3 rings: 15g total of 9ct (37.5% gold)
- 1 chain: 8g of 18ct (75% gold)
- 2 earrings: 4g of 14ct (58.3% gold)

**Calculation:**
- 9ct gold: 15g × 0.375 = 5.625g pure
- 18ct gold: 8g × 0.75 = 6g pure
- 14ct gold: 4g × 0.583 = 2.332g pure
- Total pure gold: 13.957g
- Value at £48/g: £669.94

**Dealer Offer:**
- Typically 90-95% of calculated value
- Example: £603-636 (£669.94 × 0.90-0.95)

[Understanding dealer pricing](/knowledge/gold/best-price-scrap-gold)

### Common Item Weights

**Typical Weights by Item:**

**Rings:**
- Plain wedding band: 2-4g
- Engagement ring (no stone): 3-6g
- Large statement ring: 5-10g
- Signet ring: 8-15g

**Chains:**
- Fine chain: 1-3g
- Medium chain: 5-10g
- Heavy chain: 15-30g
- Very substantial: 30-50g+

**Earrings (pair):**
- Studs: 0.5-2g
- Small hoops: 1-3g
- Large hoops: 5-10g
- Chandelier earrings: 3-8g

**Bracelets:**
- Fine bracelet: 5-10g
- Medium bracelet: 10-20g
- Chunky bracelet: 20-40g

**Coins:**
- Sovereign: 7.988g
- Britannia (1 oz): 31.1g
- Krugerrand (1 oz): 33.93g (22ct, so heavier for 1oz pure gold)

> These are rough guides. Actual weights vary significantly by design, thickness, and manufacturer. Always weigh items individually for accuracy.

## Avoiding Common Mistakes

Preventing errors in weight-based calculations.

### Mistake 1: Confusing Ounce Types

**The Problem:**
- Kitchen scale shows "1.5 oz"
- Assume 1.5 troy oz
- Calculate value as 1.5 × £1,500 = £2,250
- **Wrong!** Scale measured avoirdupois ounces

**Correct Approach:**
- 1.5 avoirdupois oz = 42.5g
- 42.5g = 1.367 troy oz
- Value: 1.367 × £1,500 = £2,050
- Difference: £200 error from confusion

**Prevention:**
- Always convert to grams first
- Use grams for all gold calculations
- Don't trust "oz" reading without confirming type

### Mistake 2: Including Non-Gold Weight

**The Problem:**
- Weigh ring with large diamond: 8g total
- Calculate value on 8g of 18ct gold
- Forget diamond weighs 2g (not gold)
- Overestimate by 25%

**Correct Approach:**
- Remove stones if possible before weighing
- Or estimate stone weight and deduct
- Only calculate gold value on gold weight
- Goldealers removes stones and weighs gold accurately

**Prevention:**
- Understand only metal weight matters for scrap
- Dealers will separate and re-weigh
- Your estimate will be rough until professional assessment

### Mistake 3: Rounding Errors

**The Problem:**
- Gold price: £1,547.83/troy oz
- Convert to grams: "about £50/g" (too rough)
- Calculate on 20g: 20 × £50 = £1,000
- **Actual:** 20g = 0.643 troy oz × £1,547.83 = £994.61
- Close, but inaccurate

**Better Approach:**
- Use precise conversion: £1,547.83 ÷ 31.1035 = £49.77/g
- Calculate: 20g × £49.77 = £995.40
- Much more accurate

**Prevention:**
- Don't round until final answer
- Use calculator with decimals
- Precision matters with high gold prices

### Mistake 4: Wrong Purity Percentage

**The Problem:**
- 9ct ring, 10g weight
- Think "9ct = 9 out of 24 = 37.5%" (correct)
- But calculate as "9/10 = 90%" (wrong!)
- Massive overestimate

**Correct Approach:**
- 9ct = 9/24 = 37.5%
- 14ct = 14/24 = 58.3%
- 18ct = 18/24 = 75%
- 22ct = 22/24 = 91.67%
- Use decimal: 0.375, 0.583, 0.75, 0.9167

**Prevention:**
- Learn the standard purities
- Double-check math
- Goldealers will test and use correct purity

[Understanding gold purity percentages](/knowledge/gold/gold-purity-hallmarks)

## Frequently Asked Questions

**Q: What's a troy ounce and why is gold measured in that instead of regular ounces or grams?**  
A: A troy ounce is a special unit of weight used for precious metals. It equals approximately 31.1 grams. It's different from the everyday ounce (avoirdupois ounce) which is about 28.35 grams. Historically, the troy ounce has been the standard for gold, silver, platinum, etc., which is why market prices are quoted per troy ounce. For example, if gold is £1,500 per troy ounce, that means about £48.23 per gram. Understanding this helps when you convert between the weight of your items and the market price. Goldealers can work with either unit, but we often find it easiest to talk in grams when evaluating jewellery and in troy ounces for bullion coins/bars.

**Q: How many grams in a troy ounce?**  
A: 1 troy ounce = 31.1034768 grams, typically rounded to 31.1 grams for simplicity. Remember this number and you can easily convert between troy ounces and grams for gold valuations.

**Q: If my kitchen scale says 2 ounces, is that 2 troy ounces of gold?**  
A: No. Kitchen scales measure avoirdupois ounces (regular ounces), not troy ounces. 2 regular ounces = about 56.7 grams = about 1.82 troy ounces. To avoid confusion, convert the reading to grams (multiply by 28.35), then you can convert to troy ounces if needed (divide by 31.1).

**Q: What's a pennyweight and do I need to know it?**  
A: A pennyweight (dwt) is an old jewellers' unit equal to 1.555 grams. You might see it on antique jewellery documents or American appraisals, but it's rarely used in modern UK transactions. If you encounter it, simply convert to grams (multiply dwt by 1.555) or let Goldealers handle the conversion. You don't need to use pennyweights when selling gold.

**Q: How do I convert the gold price from per troy ounce to per gram?**  
A: Divide the troy ounce price by 31.1035. For example, if gold is quoted at £1,500 per troy ounce, the per-gram price is £1,500 ÷ 31.1035 = £48.23/gram. This lets you estimate your jewellery's value by weight in grams.

**Q: Are Goldealers' scales accurate?**  
A: Yes. Goldealers uses professional jeweller's scales accurate to 0.01 grams (hundredths of a gram), calibrated regularly and certified for trade use. Home scales may differ by a gram or two, which is fine for estimates, but our professional scales ensure precise, fair valuations for actual transactions.

## Next Steps

Understanding weight units empowers you to estimate your gold's value and verify dealer offers confidently. Goldealers uses industry-standard measurements and transparent pricing based on accurate weights.

**Useful Resources:**
- [Complete guide to selling scrap gold](/knowledge/gold/how-to-sell-scrap-gold-uk)
- [Understanding gold purity](/knowledge/gold/gold-purity-hallmarks)
- [How gold prices work](/knowledge/gold/gold-prices-determined)

**Get a free quote from Goldealers based on professional weight measurements.**

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*Published by Goldealers Ltd · https://goldealers.co.uk/knowledge/gold/gold-weight-units-explained*