There are several standards you might be thinking of when you refer to a standard bar of gold. There is the 400oz bar of gold. This is the one you see in movies .. the one used by banks and the one that is used to store gold in Fort Knox (yes really)
The 400oz bar breaks down as 12.5 kilos and is worth a spurt above 500k with variance depending on the day (at 1700 per ounce it sits at 680k)
Then there is the singular kilo bar standard at 99.95 or 99.99% purity which is used by the personal buyer for storage and investment. This is the usual measure of storing gold for the person who uses a bank vault or safe.
This comes in at the standard multiple of a per ounce price (again for calculation purposes I am using troy ounces in a kilo at a price of 1700 which will be 32.15 times the ounce price = 54.5k
Then you arrive at the easy accumulation unit which can either be in bullion investment coin form for easy transit and accumulation, or can actually be a bullion bar .. albeit a very small one .. as an ounce is only 31.1 grams (in gold we talk Troy ounce not imperial standard)
And at 1700 an ounce a single ounce of gold is .. 1700 dollars !
If you are using in Jewellery or trying to harvest from rivers and such .. or even gold prospect (go out there and be adventurous!) you will be weighing your gold in a gram weight which at the 1700 per ounce price is 54 dollars a gram. (Divide by 31.1 to derive the per gram price)
Please note I used a fictitious market price to provide a guide to how you would calculate a price based on the amount involved and how to derive a single unit price at each level.
The amount given will fluctuate but the means of determination will not .. therefore this can continue to provide a guide.