# Bug in resistor tolerance

The resistance tolerances do not compute correctly.

Shows a 300 ohm resistor with a tolerance of 5%. The range should be plus or minus 15 ohms. The system shows it as 4.2 ohms. It also only shows the minus value, incorrectly as 295.8 ohms. The correct values would be 285 - 315 ohms.

Dear Professor @clarkj

Thank you for your message and for engaging with our forum. Your attention to detail in the calculations of resistor tolerances is greatly appreciated.

Regarding the -4.2 ohms displayed for the 300 ohm resistor with a 5% tolerance, this value is intended to represent the deviation from the nominal resistance value — in this case, indicating that the resistance is 4.2 ohms less than the nominal 300 ohms, which equates to an actual resistance value of 295.8 ohms. This is within the expected ±5% tolerance range, which would be between 285 ohms and 315 ohms.

The system’s current method displays the deviation from the nominal value, rather than the full range, to provide a direct understanding of how the specific measured value compares to the nominal value. This approach is consistent with how deviations are typically displayed in practical applications, where the focus is often on the specific value’s variance rather than the full tolerance range.

However, we appreciate your perspective and understand the importance of clarity, especially in educational contexts. We will consider how we might improve the display to ensure that it communicates the information as clearly and helpfully as possible. Thank you once again for your valuable feedback.