Oughtred is best known for his invention of an early form of the slide rule. Edmund Gunter (1620) plotted a logarithmic scale along a single straight two foot long ruler. He added and subtracted lengths by using a pair of dividers, operations that were equivalent to multiplying and dividing.
Oughtred ay pinakamahusay na kilala para sa kanyang mga likha ng isang maagang form ng slide rule. Edmund Gunter (1620) plotted a logarithmic scale kasama ang isang solong tuwid ang dalawang paa ruler ang haba. He added at bawas haba sa pamamagitan ng paggamit ng isang pares ng dibaydes, operasyon na katumbas sa multiply at naghahati.