Work in the same order every time
A repeatable routine stops silly slips:
- List the given quantities with their symbols and units.
- Convert everything to SI units first, for example cm to m and minutes to seconds.
- Write the formula in symbols before putting numbers in.
- Substitute the values with units, then solve.
- State the answer with the correct unit and a sensible number of significant figures.
Convert units before you calculate
Many lost marks are unit-conversion errors, not physics errors. Change grams to kilograms, centimetres to metres, and kilometres per hour to metres per second before substituting. Doing this first, once, is safer than trying to fix units at the end.
Keep precision until the final step
Rounding early builds up error. Carry extra digits through the working and round only the final answer. Match the significant figures to the data you were given; if the measurements have three significant figures, an answer to three is appropriate.
Check the answer makes sense
Before moving on, ask three quick questions: is the size reasonable, is the sign or direction right, and is the unit correct? A car accelerating at 500 m/s squared or a mass coming out negative is a signal to recheck. This ten-second check catches many avoidable errors.
Calculation technique is a habit, and habits form through repetition. Do a mixed set of calculation questions regularly, always showing full working, and mark them against the given answers. If you keep losing marks at the same step, a focused session on that step, with worked examples, usually fixes it quickly.