Liquid tomato feed is a concentrate you dilute into a watering can. Too weak does little, and too strong can burn roots and leaves. Enter your watering can size and the feed rate from the label to see exactly how much concentrate to add.
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What Your Result Means: the amount is the concentrate to pour into a full can of that size. Fill the can with water first, add the feed, and stir. Always follow your product label, since feed strengths differ, and use half strength for young plants.
How Much Tomato Feed per Watering Can?
It depends on your can size and the label rate. Enter both and the tool multiplies them to give the exact milliliters of concentrate to add. Fill the can with water, pour in that amount, and stir before watering.
- Enter Your Can Size, in liters or US gallons.
- Enter the Feed Rate, the milliliters per liter from your product label.
- Add the Amount, to a full can, and water at the base of the plants.
What Each Result Means
| Result | What It Tells You |
|---|---|
| Feed to add | Milliliters of concentrate for the can |
| Roughly | An easy capful or spoon estimate |
| Rate used | The dilution you entered |
Feed by Can Size
Concentrate to add at 2 milliliters per liter, a common lighter rate. Check your own label: rates vary widely, and Tomorite, for example, is 20 ml per 4.5 liters (about 4.4 ml per liter).
| Watering Can | Feed to Add at 2 ml per Liter |
|---|---|
| 2 liters | about 4 ml |
| 5 liters | about 10 ml |
| 9 liters (2 UK gallons) | about 18 ml |
| 1 US gallon (3.8 L) | about 8 ml |
How Does the Dilution Work?
The tool converts your can to liters, then multiplies by the feed rate to get the concentrate to add. A rough capful estimate helps when you have no measuring spoon.
Feed to add (ml) = feed rate per liter x liters
Rough capful estimate = feed ml divided by about 10 ml per capful
Use half the rate for seedlings and young plants
Diluting to the label strength gives plants a steady, safe dose. Guessing risks weak feeding that does little or a strong dose that scorches roots and leaves.
Worked Example
Say you have a 5-liter can and your feed says 2 milliliters per liter. The tool multiplies 2 by 5 to get about 10 ml of feed, roughly one capful, added to a full can. For a 1 US gallon can, that is about 3.8 liters, so you would add about 8 ml.
Factors That Change the Amount
- Product strength: feeds differ, so always use the rate on your label rather than a fixed number.
- Plant age: young plants and seedlings do better on half strength.
- Feeding frequency: a full-strength feed every 1 to 2 weeks (weekly in containers) or a weaker dose at every watering are both common; do not do both at full strength.
- Container versus ground: potted plants rely on feed more, since nutrients wash out faster.
- Growth stage: switch to a high-potassium tomato feed once the first fruits set.
Understanding Your Outputs
| Output | Meaning | Best Used For |
|---|---|---|
| Feed to add | Exact concentrate per can | Measuring accurately |
| Roughly | Capful estimate | Quick mixing without a spoon |
| Rate used | Your dilution | Checking against the label |
When to Use It
Use it each time you mix a can of liquid tomato feed, especially with a new product or a different can. Pair it with the feeding schedule builder for timing and the fertilizer calculator for granular feeds.
Common Mistakes to Avoid
- Eyeballing it: a splash of concentrate can be far too strong and burn the plant.
- Full strength on seedlings: young plants need half strength or less.
- Feeding dry soil: water first, then feed, so roots are not shocked by concentrate.
- Ignoring the label: rates vary between products, so read yours each time.
- Overfeeding: more feed does not mean more tomatoes and can cause soft, leafy growth.
Accuracy and Limitations
The math is exact for the numbers you enter.
What It Calculates Accurately: the concentrate to add for your can size and feed rate.
What It Does Not Know: your specific product. Always follow the label rate and cautions, and adjust for plant age and stage.
Methodology
Method: the can size is converted to liters and multiplied by the feed rate to give the concentrate to add. Inputs Used: can size, unit, and feed rate in milliliters per liter. Conversions: US gallons times 3.785 to liters; capful estimate at about 10 milliliters per capful. Default rate: 2 milliliters per liter as a starting value; label rates commonly run 2 to 5 ml per liter, with half strength for young plants. Rounding: feed to the nearest milliliter. Note: always follow your product label, since concentrations differ.
Sources: Royal Horticultural Society – Tomatoes, Iowa State University Extension – Growing Tomatoes, The Old Farmer’s Almanac – Tomatoes. Last reviewed: September 26, 2026 · Reviewed by Aiza Anwar.
Frequently Asked Questions
How much tomato feed do I put in a watering can?
Multiply your can size in liters by the label rate, often 2 to 5 milliliters per liter. At 2 ml per liter, a 5-liter can takes about 10 milliliters, roughly one capful. Always check your product label.
How often should I feed tomatoes?
With a liquid feed, feed every 1 to 2 weeks once the first fruits set, and weekly in containers. A weaker dose at every watering also works, but do not do both at full strength. Granular side-dressing in beds is every 3 to 4 weeks.
Can you overfeed tomatoes?
Yes. Too much feed causes soft, leafy growth, fewer fruit, and can scorch roots. Stick to the label rate rather than adding extra.
What is the standard tomato feed dilution?
Rates vary by product, commonly about 2 to 5 milliliters per liter; Tomorite, for example, is 20 ml in 4.5 liters. The label always comes first.
Should I feed young tomato plants?
Go easy. Seedlings and young plants do best on half strength or less until they are established and starting to flower.
Do I feed before or after watering?
Water first if the soil is dry, then apply the diluted feed. Feeding bone-dry soil with concentrate can shock the roots.
What feed is best for tomatoes?
Use a high-potassium tomato feed once the first fruits set, since potassium supports fruit development. A balanced feed is fine earlier for leafy growth.
How many milliliters is a capful of feed?
Roughly 10 milliliters, though caps vary. Use a measuring spoon or syringe for accuracy, especially with strong concentrates.
Can I feed tomatoes at every watering?
Yes, at a reduced rate, often a quarter to a half of the weekly strength. This suits containers well, but skip the extra weekly full-strength feed if you do.
Related Tomato Tools
Build a Plan with the Feeding Schedule Builder
This calculator dilutes liquid feed by the rate you enter. Products differ, so always follow your label rate and cautions. Use half strength for young plants and do not overfeed. Spotted an error? Tell us here.