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I usually divide the amount by 4 if the directions are for a gallon.  But here is some additional information that I found that may be useful.

Because liquid fertilizer formulas are concentrated and designed to be mixed with water, the container can be stored in a small area, which is useful if you're short on storage space. Because you usually apply it when you water the plants, it's particularly useful for houseplants and container plants, but you can also use it in the garden.  Concentrated liquid plant food comes in several formulas, from all-purpose formulas designed for vegetables to formulas designed for specific plants. While all complete formulas contain nitrogen, phosphorus and potassium -- known as NPK -- the ratio of these macronutrients varies. For example, an all-purpose liquid fertilizer for vegetables may be labeled 8-4-4 while one for houseplants may be labeled 8-3-8. The formula reflects the percentage of each nutrient in the concentrated formula. Each formula is designed to meet the needs of specific plants or groups of plants. Concentrated liquid plant food must be diluted with water before you use it. For houseplant formulas, this typically means 10 to 20 drops of the formula in 1 quart of water. All-purpose plant food designed for vegetables is typically diluted at a rate of 1 to 2 tablespoons per 1 gallon of water. Following the application rate is important, because using too much could harm your plants and too little won't provide enough nutrients.  (http://homeguides.sfgate.com/concentrated-liquid-plant-food-83065.html) This site also leads to a link on how to flush soil that has been overfertilized with concentrated liquid fertilizer that may be interesting to  you as well.