Plant care calculator

Potting Mix Calculator: Get the Right Perlite, Bark & Coco Coir Ratio

Calculate the ideal potting mix ratios for any plant type — from moisture-loving tropicals to drought-tolerant succulents.

Quick Answer

By factoring in your specific plant type and environmental conditions, you can precisely tailor your care routine to ensure optimal health and prevent common issues like root rot.

Updated Reviewed Reading time: 7 min

Enter your details

Enter your details below to generate a custom recommendation.

Container Details

Enter in Liters for Metric or Quarts for Metric.

Units

The Problem

Many plant owners guess at their care routines, leading to root rot, burned leaves, or stunted growth. Generic advice doesn't factor in specific plant species and local climate.

When to Use This Tool

Use this calculator when you bring home a new plant, when seasons change, or if your plant is showing signs of distress.

Who is this for?

  • Beginner houseplant owners looking to avoid common mistakes
  • Advanced collectors wanting to optimise growth rates

About this calculator

Using this calculator removes the guesswork from your plant care routine.

How to Use

  1. Select your plant type.
  2. Input your environmental conditions.
  3. Get your personalized recommendation.

The Importance of Precision

Every plant species has adapted to specific conditions in the wild. By mimicking those conditions in your home, you can dramatically increase the lifespan and vitality of your collection.

Visual Reference: Ideal Texture

High quality chunky houseplant potting mix

Chunky Aroid Mix: Notice the large pieces of orchid bark and white perlite mixed into the dark soil. This structure creates large air pockets (macropores) that prevent root rot while allowing rapid drainage.

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Potting Mix Ratio Calculator Variations & Requirements

VariationLight RequirementWatering FrequencyDifficulty
StandardBright IndirectWeeklyMedium
VariegatedHigh LightWeeklyHard
DwarfMedium LightBi-WeeklyEasy

Troubleshooting & Diagnostics Guide

1 Plant is dropping leaves despite following the recommendation

Diagnosis: Drafts, sudden temperature changes, or pest issues not related to the calculator's focus area.

Treatment: Isolate the plant, check for pests, and ensure it is away from heating/cooling vents.

Glossary of Terms

Transpiration
The process of water movement through a plant and its evaporation from aerial parts.
Photoperiod
The period of time each day during which an organism receives illumination.

Frequently Asked Questions

Is this calculator accurate for store-bought potting soil?
Yes — you can use standard store-bought indoor potting soil as the 'Base Soil' component. The calculator will tell you exactly how much perlite or bark to mix into that commercial bag to make it safe for your specific plant.
Are these soil recipes safe for sensitive plants like orchids?
Yes. When you select specific categories, the calculator drastically alters the base recipe. For example, it removes heavy soil entirely for epiphytes and replaces it with pure bark and perlite.
What is the difference between perlite and pumice?
Both are volcanic rocks used to add aeration (air pockets) to the soil. Pumice is slightly heavier, meaning it won't float to the top of the pot when you water. You can use either interchangeably in our calculator.
Why do aroids need orchid bark in their soil?
Aroids (like Monsteras and Philodendrons) are epiphytes that naturally grow on trees, not in the ground. They need massive air pockets around their roots to survive. Orchid bark provides this structure while preventing soil compaction.
Can I use outdoor garden soil instead of indoor potting mix?
No. Never use outdoor topsoil or garden dirt in indoor pots. It is far too dense, lacks necessary drainage, and almost certainly contains outdoor pests, weed seeds, and fungal pathogens that will thrive indoors.
Why is my potting mix staying wet for over two weeks?
Your mix is too heavy and lacks aeration. You need to unpot the plant and amend the soil using the 'Extra drainage' setting on our calculator, which will significantly increase the perlite and bark ratios.
Why is water running straight through the pot without absorbing?
Your soil has become hydrophobic. This happens when peat-heavy mixes completely dry out. You need to bottom-water the plant by soaking the entire pot in a basin of water for 45 minutes until the soil rehydrates.
How do I adjust this recipe for a self-watering pot?
Self-watering pots keep the bottom layer of soil constantly wet. To prevent root rot, you must increase the aeration material by 20% compared to the standard recipe. Select 'Extra drainage' to get the correct modified volume.

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