Gold bar sizes explained
Gold bar sizes range from 1 gram to 400 troy ounces (the London Good Delivery bar used by central banks). For retail buyers the practical range is 1g to 1 kilo. The right size depends on three things: how much capital you are allocating, how low you want the premium per gram, and how much flexibility you want when you eventually sell.
Common retail bar sizes and their premiums
The premium you pay above the spot price changes dramatically with bar size. Smaller bars cost more per gram, but they offer accessibility and gradual buying flexibility. Larger bars reduce the per-gram cost, but they require larger upfront capital and are less convenient to sell in parts.
The premium narrows significantly as size increases. A 1g bar might carry 12% premium, while a 1 kilo bar might carry only 1.5%. Over larger positions, that percentage difference compounds into substantial savings.
Premium comparison table in real numbers
To see the cost difference clearly, here is a breakdown at a spot price of $100/g (approximately $3,110/oz, easy to scale to current prices):
- 1g bar: $108–$115 (8–15% premium)
- 5g bar: $105–$107 (5–7% premium)
- 10g bar: $103–$105 (3–5% premium)
- 50g bar: $102–$104 (2–4% premium)
- 100g bar: $101–$103 (1–3% premium)
- 1000g bar: $100.50–$102 (0.5–2% premium)
The cost of flexibility: Buying 10 × 10g bars costs more than 1 × 100g bar for the same gold weight. At $100/g, 10 × $104 = $1,040 versus 1 × $102 = $1,020. That $20 difference represents the cost of flexibility — the ability to sell in smaller portions later, or to gift individual bars without liquidating your entire position.
For smaller buyers (under £5,000 total position), that flexibility is worth the premium. For larger buyers (£50,000+), the cumulative savings from larger bars become significant enough to justify the concentration.
The 1 oz vs 1 kilo bar decision
These two formats represent opposite ends of the retail spectrum and define the buying conversation for most people.
1 oz (31.1g): The global retail standard. Easiest to compare across refiners and dealers. Strong resale anywhere in the world. Typical premium: 2–4%. Most widely stocked format. Good for buyers who want to build positions gradually or sell in chunks without committing a large capital amount upfront.
1 kilo (1000g): The lowest-premium retail format. Requires larger capital commitment. Harder to partially liquidate without finding a buyer for the full bar. More efficient for buyers building larger positions over time and planning to hold for 5+ years.
Sweet spot for most buyers: 1 oz or 100g bars. This range balances premium efficiency (around 2–3% over spot) with practical flexibility. You can build a position incrementally, and you can sell portions without difficulty.
When to choose kilo: When buying 5+ oz at a time and planning to hold 5+ years without needing partial liquidation. The per-gram savings compound over larger quantities, but only if you can commit the capital and accept the concentration risk.
What to look for in any bar
Regardless of size, every gold bar should carry identifiable markings that prove authenticity and allow you to resell it confidently. Here is what to check:
- LBMA accredited refiner stamp: Look for refiners like PAMP, Heraeus, Argor-Heraeus, Perth Mint, Royal Mint, or Metalor. These are the global standard and carry instant credibility.
- Weight and purity stamped on bar: Should read "999.9" or "24K" (or equivalent). All investment bars should be at least 99.5% fine (often stamped as 995 or higher).
- Unique serial number: All bars 1g and above from major refiners should have a serial number that allows traceability.
- Certificate of authenticity / assay card: Bars in blister packaging should come with an assay card showing the refiner's signature, weight, and purity. This card is essential for resale.
- Matching serial numbers: If your bar came with packaging and an assay card, the serial number on the bar, packaging, and card should match. Mismatches are a red flag.
Bars from major refiners are unlikely to be counterfeited because the refining cost to fake a small bar is not economical. The real risk in buying secondhand is a bar with an unverifiable history or missing documentation. Always buy new bars from reputable dealers and keep your assay cards safe.