MB HydroCalc

This calculator was designed to calculate how much nutrient-solution (fertilizer water) you will need to mix up to grow vegetables using MasterBlend's 4-18-38 tomato formula. This fertilizer can be used to grow vegetables with the "Kratky Method", using Dutch Buckets, or many other hydroponic methods.

To use the hydroponic fertilizer calculator you need to know either the dimensions of your container or the number of gallons it holds. We determine the correct amount of nutrients needed based on the total gallons amount.

Within the App, you can change from calculating Nutrients to calculating Water Volume by switching between the tabs at the top of the screen.

If you made a custom rectangular grow bed, you can input the inside dimensions into the Water Volume Calculator to find out how many gallons it holds. The number will carry over to the Fertilizer Calculator. Just remember that when using the Kratky Method, only 1/8-inch (or so) of your net pot should be underwater at the start of your grow.

If you already know how many gallons your containers hold, you can simply enter that number into the Water Volume field of the Fertilizer Calculator. The correct ingredient amounts will be calculated for you in Grams once you select either Lettuce or Tomatoes. It is important to weigh out the fertilizer using a scale so you don't over fertilize and kill your plants. Ideally, you would want the pH levels of your final solution to be around 6.4 - 6.7. You can research what your plants like best and check your solution using a pH meter.

While the calculator lists only a Tomato and Lettuce formula, the same two formulas have been successfully used with other vegetables as well. You can easily grow various types of peppers with the Tomatoes formula, and other leafy greens like kale work great with the lettuce formula.