Micro lots, rounding, and what a pip is really worth

[Shadow Trader]

Position size calculators spit out numbers like 0.137 lots, and then the platform quietly does something else with them. A few overlooked details:

- Volume step. Most servers accept volume only in fixed increments, such as 0.01. A size of 0.137 gets rounded or rejected depending on the platform, and rounding down versus to the nearest changes risk by several percent on small accounts.
- Minimum lot. If the calculated size falls below the minimum, the order either fails or gets pushed up to the minimum, which means actual risk exceeds the plan.
- Pip value is not a round number. On a 0.01 lot a pip may be worth roughly a tenth of a dollar on some pairs, but on crosses it is derived from another rate, so the figure floats and rarely matches a fixed rule of thumb.
- Account currency. If the account is not in the quote currency, each pip converts at the current rate, so the same lot size has a slightly different value each hour.
- Fractional pips. With a fifth decimal, a pip and a pipette are different things, and a stop a few points away can be a fraction of a pip that the spread alone already covers.
- Display rounding. Profit shown to two decimals on a micro lot can hide a loss of a few cents per trade that adds up across hundreds of scalps.

On tiny accounts the rounding error is a large percentage of the intended risk.

Checking the symbol specification for minimum volume, step and tick value takes a minute and avoids most of these surprises.

Which of these has actually thrown off a trade size on your account?