The amount of 2,4-D herbicide to use per gallon of water depends on the specific product concentration and the type of weeds you're targeting. Always consult the product label for the manufacturer's recommended dilution rates. Typically, you'll find instructions for mixing a certain number of ounces or tablespoons of 2,4-D per gallon of water. Following the label instructions carefully is crucial for effective weed control and to avoid damaging desired plants. Remember to wear appropriate safety gear when handling herbicides.