There's a few times in this series where I'll introduce a foundational concept that's so significant, I'll suggest that you say it out loud to yourself. Here's the first one, say it with me:

"Everything in analog is imperfect. Everything in analog is at least slightly innaccurate. Everything."

You can buy more accurate, lower tolerance resistors, as you can with all the other components we'll get into. You can also buy more accurate multimeters and test equipment. But they're more expensive.

5% tolerance is pretty standard for resistors, it's rare that you'll need anything else. I believe the only time I've ever needed resistors that were more accurate was when designing a 1 volt per octave control voltage circuit for a synthesizer, in which I wanted the tuning to be as accurate as possible.

For each unit, I had to get two 0.01% tolerance resistors. They were around $2.50 each, whereas a standard 5% resistor is usually 10 cents or less! A 2400% price increase!