打算盘

You can use it as a verb phrase. If someone is being sneaky, say they are 打算盘. You can also describe the quality of their plan. A 'loud' abacus 算盘打得响 means they are very obvious about their greed. A 'fine' abacus 精打细算 means they are very careful with money. It is a very flexible phrase for social dynamics.

Use it when a friend is trying to get a better deal. Use it when a coworker is maneuvering for a promotion. It is perfect for office politics. You can also use it at the market. If a vendor is overcharging, they are definitely 打算盘. It adds a bit of flavor to your observation of people's motives.

Do not use it for simple classroom math. If a kid is doing 2+2, they aren't 打算盘. Avoid it in very tragic or solemn situations. If someone is planning a funeral, don't say they are 打算盘. It can sound a bit cynical or suspicious. Use it for business, money, or social strategy instead.

The abacus was the calculator of ancient China. For centuries, it was the symbol of the merchant class. Because merchants were often seen as shrewd, the tool became a metaphor. Even though we use iPhones now, the image of the clicking beads remains. It represents the 'old school' way of being smart with resources. It is deeply tied to the Chinese value of thrift and strategy.

The most famous variation is 如意算盘. This means a 'wishful' abacus or 'wishful thinking.' It is used when someone's plan is too perfect to be true. Another is 打小算盘. This means being petty or selfish in a small way. If you are being very frugal, you are 精打细算. Each variation changes the 'flavor' of the calculation.