Fertilizer Dilution Calculator
Work out how much liquid fertilizer to mix into your water at full, half, or quarter strength.
When in doubt, dilute more, not less. Never fertilize bone-dry soil, water first. Skip or halve feeding in winter for most houseplants.
How it works
Enter how much water you're mixing up, the label rate printed on your fertilizer bottle (in ml per liter), and how strong you want the mix. The calculator multiplies water by label rate by a strength factor: full strength uses the whole label amount, half strength cuts it in half, and quarter strength uses a quarter. Most houseplants do better on half or quarter strength fed more often than full strength fed occasionally, since a weaker, steadier feed is easier on roots than an occasional strong dose.
Worked example: you're watering 2 liters, your label says 5 ml per liter, and you're feeding at half strength. That's 2 times 5 times 0.5, which comes out to 5 ml, or about 1 teaspoon. Mix that into your 2 liters of water and use it in place of a plain watering.
FAQ
Why dilute more than the label says?
Fertilizer labels are often written for outdoor garden beds or heavy feeders growing in full sun, not a pothos on a shelf. Houseplants generally grow slower and can burn at full strength, showing up as crispy brown leaf edges. Diluting further and feeding more often gives a steadier supply without that risk.
Can I fertilize a plant that just got repotted?
Wait a few weeks. Fresh potting mix usually has enough nutrients on its own, and roots disturbed by repotting are more sensitive to fertilizer salts until they settle back in.
What if I forget to feed for a month or two?
Just pick back up at your normal schedule. There's no need to double the next dose to catch up. Consistent light feeding works better than trying to make up for missed rounds.
Do I need to feed in winter?
Most houseplants slow their growth in winter as light drops, so they need little or no fertilizer during that stretch. Skip feeding entirely or cut it back to quarter strength once a month until spring growth picks back up.
For more on building a feeding routine (and reading your plant's other needs alongside it), see how to fertilize houseplants the right way, how to care for houseplants in winter, and how often to water houseplants.