The accuracy of measurement is determined primarily by the percentage error, which compares the difference between the measured value and the actual value relative to the actual value. This tells how close the measured value is to the true value. Several factors influence measurement accuracy, including:

• Calibration of instruments to maintain correctness
• Environmental conditions such as temperature, humidity, and pressure
• Stability and linearity of the instrument's response
• Sensitivity and resolution of the measuring instrument
• External interferences like electromagnetic fields or vibrations
• Human factors such as technique and reading errors
• Instrument limitations and drift over time

Overall, minimizing percentage error and controlling these factors help achieve higher measurement accuracy.