Free Plant Calculators
Simple tools for everyday plant care. They run instantly in your browser, with no sign-up and no AI doing the thinking. Pick a calculator to get started.
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Watering Schedule
How often (and how much) to water, based on your pot, light, and season.
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Pot & Soil Volume
Work out a pot’s volume and exactly how much potting soil it needs.
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Soil Mix Recipe
Scale the perfect aroid, succulent, or fern mix to your exact pot volume.
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Fertilizer Dilution
Dilute liquid fertilizer to full, half, or quarter strength without guessing.
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Grow Light / DLI
Turn PPFD and hours-on into Daily Light Integral and check it’s enough.
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Repotting Size
Find the right next pot size so you upsize without drowning the roots.
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Humidity Helper
Compare your room’s humidity to what your plant wants and fix the gap.
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Light Level
Translate a lux reading or window into a real light category for plants.
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Plants per Room
Estimate how many plants a room needs for a noticeable green boost.
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Frost / Outside Check
Check tonight’s low against your plant’s cold tolerance before moving it out.
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Plant care, minus the guesswork
Most houseplant problems come down to a few numbers: how often to water, how big the next pot should be, whether a spot has enough light, and how much fertilizer to mix. These free calculators turn those questions into clear answers in a few seconds, using the same formulas and rules of thumb experienced growers rely on. They default to US units (inches, quarts, gallons, °F), with metric available in every dropdown.
Built to be fast and private
Every tool runs entirely in your browser. Nothing you type is sent to a server, and the answers come from plain math you can check rather than from an AI guess. That also means they load quickly and keep working even if your connection drops.
Where calculators fit in
Calculators give you a strong starting point, but every home is different. Pair them with our plant care guides for technique, the plant profiles for species-specific needs, and the gear guides when you need to choose a humidifier, grow light, or potting mix.
Frequently Asked Questions
Are these plant calculators free?
Yes, every calculator on this page is completely free. There is no account to create, nothing to download, and no usage limit. Each one runs in your web browser, so you can use them as often as you like.
Do the calculators use AI?
No. They use fixed horticultural formulas and well-established rules of thumb, so the same inputs always give the same answer. Because the math runs in your browser, the tools also keep working if your connection drops.
Which plant calculator should I use first?
Start with the watering calculator if you are unsure how often to water, since overwatering is the most common way houseplants die. After that, the pot and soil volume and light level tools are the ones most people reach for next.
Are the results exact for my specific plant?
Treat them as reliable starting points rather than absolute rules. Pot size, light, season, and your home all shift the numbers, so check the soil and watch your plant. For species-specific guidance, open that plant’s care guide.
