Free feed chart tool
Cannabis nutrient calculator
Pick your nutrient line, grow medium and setup. Get the published mL per gallon rate for every week, the exact amount to measure into your water, and the total product your grow needs from seed to harvest.
Step 1 of 4: Nutrient line
How to use the cannabis nutrient calculator
The calculator turns a feed chart into a number you can measure. It does not guess and it does not average. It reads the published mL per gallon rate for the line and week you pick, then multiplies that rate by the amount of water you are mixing.
- Pick your nutrient line. Classic 3-Part for photoperiod grows, Bonnie and Clyde for autoflowers, PuurOrganics for an OMRI certified organic feed.
- Set up your grow. Choose your medium, how many plants you run, your pot size and how often you feed. Pot size and plant count decide how much water you mix per feeding. If you mix into a fixed reservoir instead, type that amount into the water override and the whole schedule recalculates around it.
- Choose your additives. Core products for the line are always in. Additives are opt in, and the ones dosed once per week are counted that way in your totals.
- Read your schedule. You get a week by week table of exact mL amounts, a target pH for every stage, and the total volume of each product the whole grow will use.
How to read mL per gallon
Feed charts are written in mL per gallon. That is millilitres of product for every gallon of water in the mix, not per plant and not per pot. To get the amount you actually measure, multiply the rate by the gallons of water you are mixing.
Worked example. Classic 3-Part, week 5, Pre-Flower. The chart calls for Micro at 5 mL per gallon. Mixing 5 gallons means 5 x 5, so 25 mL of Micro goes into the container. Bloom at the same week is also 5 mL per gallon, so that is another 25 mL. The calculator does this for every product and every week at once.
Working in litres instead? One U.S. gallon is 3.785 litres, so divide the chart rate by 3.785 to get mL per litre. A 5 mL per gallon rate is roughly 1.3 mL per litre. The unit switch in the calculator handles the conversion for you.
The strength slider scales every number at once. Below 0.8 is a light feed for seedlings and sensitive plants, 0.8 to 1.2 is the standard chart rate, and above 1.2 is a heavy feed for growers who know how their plants respond. If you are unsure, feed light and work up.
Mixing order matters
Nutrient concentrates react with each other if they meet before they are diluted. Add one product at a time to the water, stir until it disperses, then add the next. Never pour two concentrates together.
Classic 3-Part and additives
- Fill the container with water first.
- Add Micro first. This prevents nutrient lockout.
- Add Grow.
- Add Bloom.
- Add CalMag if you are using it.
- Add any other additives.
- Adjust pH last, once everything is in.
PuurOrganics
- Fill the container with water first.
- Add PuurBalance first, because the amino acids help uptake.
- Add PuurCalMag.
- Add PuurNitro, then PuurPhos, then PuurK.
- Add any other additives.
- Adjust pH last.
Cloudiness in a mixed PuurOrganics solution is normal, it is organic particulate. If you hold it in a reservoir, use it within two to four days.
Autoflowers
Never mix Bonnie and Clyde together. They are stage specific: Bonnie carries the vegetative feed and Clyde carries the flowering feed. Switch from Bonnie to Clyde at the first sign of flowering, when pistils show. CalMag is essential for autoflowers rather than optional, which is why the calculator turns it on by default for this line.
Target pH by medium
Two different pH sources appear on this page, and they do not fully agree. The weekly range shown with your schedule is the range printed on the feed chart for that line and week. The table below is the general working band for each medium, from the medium guides. In the early weeks the chart ranges run below the soil band in this table.
Until the two are reconciled, treat them as two inputs rather than one answer. Check the official charts for your line before you adjust, and go by what your plants and your runoff tell you.
| Medium | Target pH | Notes |
|---|---|---|
| Soil | 6.0 to 7.0 | The widest workable range of the three. |
| Coco | 5.5 to 6.5 | 5.8 is a common target. |
| Hydro | 5.5 to 6.0 | The tightest range, check it often. |
Always set pH after every nutrient and additive is in the water. Adjusting first and then dosing will move the reading.
Frequently asked questions
How much nutrient do I use per gallon?
It depends on the line and the week. On the Classic 3-part chart, Micro runs 1.25 mL per gallon at seedling and steps up to 5 mL per gallon through flower, while Bloom peaks at 7.5 mL per gallon in late flower. Pick your line and week in the calculator above and it reads the published rate straight off the chart, then multiplies it by the water you are mixing.
What order should I mix Cronk nutrients in?
For the Classic line: fill your container with water, add Micro first to prevent lockout, then Grow, then Bloom, then CalMag if you are using it, then any other additives, and adjust pH last. For PuurOrganics: water first, then PuurBalance, PuurCalMag, PuurNitro, PuurPhos, PuurK, then other additives, and pH last. Add one product at a time and stir between each one. Never pour concentrates together.
Can I mix Bonnie and Clyde in the same reservoir?
No. Bonnie and Clyde are stage specific and should never be mixed together. Bonnie carries the vegetative feed and Clyde carries the flowering feed. Switch from Bonnie to Clyde at the first sign of flowering, when pistils show.
What pH should I feed at?
The calculator shows the pH range printed on the feed chart for the line and week you picked. Separately, as a medium level guide, soil runs 6.0 to 7.0, coco runs 5.5 to 6.5 with 5.8 a common target, and hydro runs the tightest at 5.5 to 6.0. These two sources disagree in the early weeks, where the chart ranges sit below the soil band, so check the official charts for your line before you adjust rather than treating either number as final. Always adjust pH after all nutrients and additives are in the water.
How do I convert mL per gallon to mL per liter?
Divide by 3.785, because one U.S. gallon is 3.785 liters. A 5 mL per gallon rate works out to roughly 1.3 mL per liter. You can also switch the calculator to liters and it will handle the conversion for you.
Do I need CalMag?
For autoflowers it is essential rather than optional, which is why the calculator turns CalMag on by default for the Bonnie and Clyde line. For the Classic line it is optional but recommended, especially if you are feeding with RO or very soft water. PuurOrganics uses PuurCalMag, which is treated as part of the base feed rather than an add-on.
Does the calculator change the dose for coco or hydro?
No. It reports the published feed chart rate and multiplies it by your water volume, whichever medium you pick. The medium selector is there so your saved mix record is complete, and so you know which pH band to aim for. Watch your plants and your runoff, and adjust with the strength slider rather than assuming a medium multiplier.
Want the raw charts instead of the tool? Read the feeding charts for Cronk Nutrients lines.