Liquid Fertilizer Dilution Calculator
Mix liquid or water-soluble fertilizer to the label dose per gallon for your watering can, and total it across a season of feedings.
How it works
Per batch = dose per gallon × water gallons · Season total = per batch × feedings
Water-soluble and liquid fertilizers are dosed per gallon, so a batch needs the label rate times the water volume. Under-feeding is easy to correct, but over-feeding is not — excess soluble salts burn roots and leaf tips and build up in the soil, so it is safer to stay at or slightly below the label rate and feed more often. Water the soil, not the foliage, unless the label calls for a foliar feed.
Worked example
At 1 tablespoon per gallon in a 2-gallon watering can, mix 2 tablespoons per batch. Over a season of 6 feedings that totals 12 tablespoons (about 0.75 cup) of fertilizer.
Frequently asked questions
What happens if I use too much fertilizer?
Excess fertilizer is soluble salt, which pulls water out of roots and causes “fertilizer burn” — brown, crispy leaf edges and stunted growth. When in doubt, dilute more and feed more frequently rather than dosing heavily.
How often should I feed?
It depends on the plant and product — many liquid feeds are used every one to two weeks during active growth and paused in winter. A weaker mix applied more often is gentler than an occasional strong dose.
Can I mix a big batch and store it?
It is best to mix only what you will use in a session. Diluted fertilizer can grow algae or lose potency in storage, and the numbers here make it easy to size each batch to your watering can.
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This calculator is for educational purposes. Double-check important results before acting on them.