London gold profit and loss calculation can first capture three quantities: price changes, contract units of 100 ounces per lot, and trading lots. Buy position with the closing selling price minus the opening buying price; Sell the position by subtracting the closing purchase price from the opening selling price.

Example of buying position

Assuming buying 0.1 lots of London gold, the opening bid price is $4300.15, and then closing the position at the selling price of $4310.00.

The price change is $9.85.

The theoretical profit and loss is approximately 9.85 × 100 × 0.1=98.5 US dollars.

Example of selling position

Assuming a 0.1 lot short position is established at the sell price of $4300.00, and then closed at the buy price of $4290.15.

The price change is also $9.85.

Theoretical profit and loss is approximately $98.5.

Why can't we use the same quotation for calculation

Because long and close positions, short and close positions use different side quotes. The spread is already included between the bid and ask prices.

If you only look at one price on the candlestick, the manual calculation result may not match the trading record.

What else do I need to add to my overnight position

After the order crosses the settlement time, overnight fees may also be incurred. When holding for multiple days, this part needs to be separately included.

Therefore, the most complete review should be based on the actual closing results, and formulas are more suitable for quick estimation.

First calculate the risk, then calculate the goal

You can use the same formula in reverse before opening the warehouse.

For example, with 0.1 lots and a planned stop loss distance of $15, the theoretical risk is approximately $150. If this number exceeds one's tolerance range, one should first reduce the number of hands instead of waiting until the position is opened before finding a solution.

First, calculate a buy order

Assuming the London gold buying price is $4300.15, you buy 0.2 lots. Afterwards, the selling price rose to $4312.00 and the position was closed. The long price difference is 4312.00 minus 4300.15, resulting in $11.85.

0.2 lots correspond to 20 ounces, so the theoretical price change amount is 11.85 × 20, approximately $237. Here, we will ignore other items such as overnight fees in order to clarify the basic formula.

Calculate another sales order

Assuming you short 0.2 lots at a selling price of $4310.00, and then gold falls, the buying price reaches $4298.15. The short selling price difference is 4310.00 minus 4298.15, which is also $11.85.

Multiplying by 20 ounces, the theoretical price change is also about $237. The direction is different, but as long as the price moves in a favorable direction for the position, the formula can ultimately be summed up as "favorable price difference x contract quantity".

If the direction is wrong, how do the numbers change

If you buy with an additional order of 4300.15 and later sell at a price drop of 4290.00 US dollars, the price difference is negative 10.15 US dollars. 0.2 lots correspond to 20 ounces, with a theoretical floating loss of approximately $203.

Short selling, on the other hand, creates an unfavorable price differential when prices rise. The most common mistake when looking at formulas is reversing the subtraction order of long and short directions, so the first step in reviewing is always to look at the order direction first.

Why is there a slight difference between manual calculation and account results

The actual results of the account may also include factors such as overnight interest rates and actual transaction prices. If the position crosses the settlement time, corresponding overnight fees need to be added; When the market changes rapidly, the actual transaction price of the order may also differ from the quoted price selected during manual calculation.

Therefore, manual calculation is suitable for verifying logic and position size, and the final bill is still based on transaction history. Especially before and after the release of major data, do not rely solely on a price point in the screenshot to infer the transaction result.

Suggest simplifying the formula into one sentence

For long orders, look at "closing selling price minus opening buying price", for short orders, look at "opening selling price minus closing buying price", then multiply by 100 ounces and the number of lots. Remember this sentence, the vast majority of London gold base profits and losses can be self reviewed.

For each trade, it is best to keep the "plan" and the "result" separate

Before opening a position, first work out the theoretical risk: the lot size, the stop-loss in dollars, and the maximum amount you are willing to lose. After closing, work out the actual result: the actual entry price, the actual exit price, overnight fees and the final profit or loss. This shows whether the problem lies in your judgement, your execution or your costs. When reviewing over the long term, if you only record "made 237 dollars", it is hard to tell whether the trade was executed according to plan; only by recording the planned risk as well can you see whether the returns were built on an oversized position.

Risk warning: the example does not include all fees or actual execution differences, and is intended only to illustrate the calculation logic.

先算一笔买入订单

假设伦敦金买入价4300.15美元，你买入0.2手。之后卖出价上涨到4312.00美元并平仓。做多价格差为4312.00减4300.15，得到11.85美元。

0.2手对应20盎司，所以理论价格变化金额为11.85×20，约237美元。这里先忽略隔夜费用等其他项目，目的是把基础公式算清楚。

再算一笔卖出订单

假设你在卖出价4310.00美元做空0.2手，后来黄金下跌，买入价来到4298.15美元。做空价格差为4310.00减4298.15，同样是11.85美元。

乘以20盎司，理论价格变化也约237美元。方向不同，但只要价格朝持仓有利方向移动，公式最终都可以归结为“有利价格差×合约数量”。

如果方向错了，数字怎么变

如果多单4300.15买入，后来卖出价跌到4290.00美元，价格差为负10.15美元。0.2手对应20盎司，理论浮亏约203美元。

做空则相反，价格上涨会形成不利差额。看公式时最容易出错的是把多空方向的减法顺序弄反，所以复盘第一步永远先看订单方向。

为什么手算和账户结果会有小差别

账户真实结果可能还有隔夜利息、实际成交价等因素。如果持仓跨过结算时间，需要加入对应的过夜费用；行情快速变化时，订单实际成交价也可能与手算时选取的报价存在差异。

因此手算适合用来检验逻辑和仓位规模，最终账单仍以交易历史为准。尤其是在重大数据公布前后，不要只凭截图中的某个价格点反推成交结果。

建议把公式简化成一句话

多单看“平仓卖出价减建仓买入价”，空单看“建仓卖出价减平仓买入价”，再乘100盎司和手数。把这句话记住，绝大多数伦敦金基础盈亏都能自己复核。

一笔订单最好把“计划”和“结果”分开

建仓前可以先算理论风险：手数多少、止损多少美元、最多愿意承担多少钱。平仓后再算实际结果：真实建仓价、真实平仓价、隔夜费用和最终盈亏。这样可以看出问题到底出在判断、执行还是成本上。长期复盘时，如果只记“赚了237美元”，很难知道这笔交易是否按计划执行；把计划风险也记录下来，才看得出收益是不是建立在过大仓位上。

风险提示：示例未计入所有费用和实际成交差异，仅用于说明计算逻辑。