Modest differences in conduct can lead to wildly different legal outcomes. A person deemed slightly negligent when harming another may owe millions of dollars. Had the person been just a bit more cautious, he would owe nothing. Similarly, when self-defense is deemed slightly negligent, a person may spend several years in prison. Had the person been just a bit more cautious, he would have no criminal liability at all. Though the law must draw difficult lines, the lines need not have (...) such startling effects. We can adjust damage awards and the severity of prison sentences anywhere along a spectrum. -/- A legal input and output have a “smooth” relationship when a gradual change to the input leads to a gradual change to the output. The prior examples are not smooth but “bumpy”: a gradual change to the input sometimes dramatically affects the output and sometimes has no effect at all. The law is full of these bumpy relationships that create hard-to-justify discontinuities. -/- In this Essay, I discuss the relative advantages of smooth and bumpy legal relationships and explain how the choice of an input-output relationship differs from the choice between rules and standards. I argue that smooth relationships will often create less “rounding error” than bumpy relationships by more closely approximating our underlying moral norms. (shrink)