Cannabis Grow Room Calculator

Estimate your yield, electricity costs, timeline, and recommended setup for indoor and outdoor cannabis cultivation

Grow Type

Space Dimensions & Lighting

Lighting Type

Growing Details

Growing Medium

Strain Type

Planning Your Cannabis Grow: What to Know Before You Start

Growing cannabis at home has become increasingly accessible as more states legalize personal cultivation. Whether you are setting up a closet grow with a single LED light or planning a full-scale indoor garden, understanding the variables that affect yield, cost, and timeline is essential for a successful harvest. Our grow calculator takes the guesswork out of planning by estimating your expected results based on space dimensions, lighting type, growing medium, strain selection, and number of plants.

Lighting is the single most important factor in indoor cannabis cultivation. Modern LED grow lights offer the best efficiency, producing one to two grams of dried flower per watt of power consumed. High-pressure sodium lights remain popular for their proven performance but generate more heat and consume more electricity. The size of your grow space determines how many lights you need and how many plants you can comfortably fit without overcrowding, which directly impacts airflow, plant health, and final yield. For outdoor grows, your local climate and the number of sunlight hours during the growing season play the dominant role.

Your choice of growing medium also has a measurable impact on results. Soil is the most beginner-friendly option and produces excellent terpene profiles. Coco coir provides faster growth rates and a roughly ten percent yield increase over soil by improving oxygen availability at the root zone. Hydroponic systems push growth rates even higher but require more equipment, monitoring, and experience to manage properly. Use the calculator above to model different scenarios and find the setup that matches your goals, budget, and experience level before you invest in equipment.

Frequently Asked Questions

How much cannabis can one plant yield?
Yields vary significantly based on growing conditions. Indoor plants under LED lighting typically produce 100 to 300 grams each, while well-maintained outdoor plants in warm climates can yield 500 to 1000 grams or more. Factors like genetics, lighting, nutrients, container size, and growing experience all influence the final harvest weight.
How much does it cost to grow cannabis at home?
Initial setup costs range from a few hundred dollars for a basic soil grow to several thousand for a fully equipped indoor grow room with LED lights and ventilation. Monthly electricity costs for a small indoor grow with LED lights typically run 30 to 80 dollars depending on your local rates and the number of lights. Outdoor grows have minimal ongoing energy costs.
How long does it take to grow cannabis from seed to harvest?
The total timeline from seed to harvest depends on the strain type and growing method. Auto-flowering varieties can finish in as little as 8 to 10 weeks total. Photoperiod indica strains typically take 12 to 16 weeks including a 4-week vegetative phase and an 8 to 10 week flowering phase. Sativa strains may need 16 to 24 weeks due to their longer flowering period.
Is it legal to grow cannabis at home?
Home cultivation laws vary by state and country. Many recreational-legal states permit adults to grow a limited number of plants, often 4 to 6 per household. Some medical states allow patient cultivation with a valid card. However, several states that have legalized cannabis for adult use still prohibit home growing. Always check your local and state regulations before starting a grow.
Which growing medium produces the best yields?
Hydroponic systems generally produce the highest yields, often 15 to 20 percent more than soil, because they deliver nutrients directly to the roots and allow for precise environmental control. Coco coir offers a balance between soil simplicity and hydroponic performance, typically yielding around 10 percent more than soil. Soil is the most forgiving medium for beginners and produces excellent flavor profiles.