Grow Light Coverage Calculator
Enter the length of your grow space in feet.
Enter the width of your grow space in feet.
Select your grow light type for tailored recommendations.
Calculated as: Length × Width
Based on room area and light type.
Estimated light intensity for optimal growth.
Suggested distance from plants based on light type.
Enter the length of your tent.
Enter the width of your tent.
Enter the height of your tent.
Calculated as: Length × Width × Height
Number of air exchanges per hour.
Efficiency of your inline fan (as a decimal).
Select if you are supplementing CO₂.
Calculated as: (Room Volume × Air Exchange Rate) ÷ Fan Efficiency. Adjusted for CO₂ if needed.
Enter the wattage of your grow light.
Number of hours the light runs per day.
Cost per kilowatt-hour.
Calculated as: (Wattage × Hours ÷ 1000) × Rate
Approximate cost per month (daily cost × 30)
Approximate cost per year (daily cost × 365)
Last Updated: June 9, 2025
Grow Light Coverage Calculator & Distance Guide for Indoor Plants
Created by James S. Lockwood
With a background in botany and ecological sciences, James specializes in creating practical tools and resources to help gardeners, farmers, and plant enthusiasts optimize their green spaces.
When it comes to indoor gardening, getting your lighting right makes all the difference. Whether you’re growing in a small tent or a larger dedicated room, this Grow Light Coverage Calculator helps you figure out exactly how much light you need—and how high to hang it for the best results.
Table of Contents
Why Grow Light Coverage Matters?
Plants thrive when they receive the right amount of light at the right intensity. Too little, and they stretch or stay stunted. Too much, and you risk light burn or wasting electricity. That’s where this tool comes in—it gives you wattage and PPFD estimates based on your grow space and light type.
How to Use the Grow Light Coverage Calculator?
Using the calculator is simple and intuitive:
Enter Your Room Dimensions:
Input the length and width of your grow room or tent in feet. This determines the total square footage your lights need to cover.Choose Your Light Type:
Select whether you’re using LED, HPS, MH, or Fluorescent grow lights. Each has a different intensity and coverage footprint.Get Your Results Instantly:
The calculator shows your room area in square feet.
You’ll also see a recommended wattage range tailored to your space and light type.
It gives a PPFD estimate—a measure of how much usable light your plants receive.
Plus, it suggests ideal hanging heights depending on whether your plants are in the seedling, veg, or flowering stage.
✅ This tool helps you dial in your setup without the guesswork.
How Much Light Do Your Plants Need?
Grow lights mimic natural sunlight. Use this calculator to determine the right wattage and PPFD levels for each growth stage.
Recommended Wattage & PPFD (Light Intensity)
2x2 ft
💡 100-150W Recommended Wattage
🌱 400-600 PPFD (µmol/m²/s)
4x4 ft
💡 400-600W Recommended Wattage
🌱 600-900 PPFD (µmol/m²/s)
8x8 ft
💡 1,200-1,500W Recommended Wattage
🌱 900-1,200 PPFD (µmol/m²/s)
Grow Light Distance Calculator: Finding the Perfect Hanging Height
Different lights need to be hung at different distances from your plants. Here’s a quick breakdown:
LED
🌱 Seedling: 24-30"
🌿 Veg: 18-24"
🌸 Flower: 12-18"
HPS
🌱 Seedling: 36-48"
🌿 Veg: 24-36"
🌸 Flower: 18-24"
MH
🌱 Seedling: 24-30"
🌿 Veg: 18-24"
🌸 Flower: 12-18"
Fluorescent
🌱 Seedling: 18-24"
🌿 Veg: 18-24"
🌸 Flower: 18-24"
📌 Note: Always monitor your plants after adjusting light height. Leaf curling or bleaching? Back the lights off a bit.
Built-In Tools to Go Further
Beyond light coverage and distance, the calculator also includes:
🌬️ Grow Tent Ventilation Calculator
If you’re growing in a tent, proper airflow is just as important as light. Input your tent dimensions, air exchange rate, and fan efficiency—and get a precise CFM (Cubic Feet per Minute) recommendation. It even adjusts if you’re enriching with CO₂.
💡 Grow Light Electricity Cost Estimator
Worried about energy bills? Plug in your light’s wattage, daily runtime, and your local electricity rate. You’ll get an estimate of your daily, monthly, and yearly cost—so there are no surprises at the end of the month.
Why Ventilation is Important for Grow Rooms?
Ventilation ensures optimal air circulation, temperature control, and CO₂ levels. Without proper airflow, plants suffocate, overheat, or become moldy.
CFM (Cubic Feet per Minute) Calculation Formula
Grow Tent Ventilation Requirements
2x2x5 ft
🌬️ 50-100 CFM Recommended CFM
4x4x6 ft
🌬️ 200-250 CFM Recommended CFM
8x8x8 ft
🌬️ 500-700 CFM Recommended CFM
🔹 Choose a fan that meets or exceeds the required CFM for efficient air exchange.
CO₂ Supplementation & Its Impact on Ventilation
CO₂ is a growth booster but affects ventilation needs. Use this calculator to adjust CFM based on CO₂ levels.
CO₂ Ventilation Adjustment Chart
No CO₂
🌬️ 250 CFM Required CFM
CO₂ Enriched
🌬️ 150 CFM Required CFM
🟢 Pro Tip: Plants grow faster at 1200-1500 ppm CO₂ when air exchange is controlled.
How Much Does It Cost to Run Grow Lights?
Indoor gardening can increase electricity bills. Use this calculator to estimate your daily, monthly, and yearly costs.
Electricity Cost Formula
Grow Light Energy Cost Chart
LED
💡 600W Wattage
⏳ 18 hrs per Day
💰 $39.31 per Month
HPS
💡 1000W Wattage
⏳ 12 hrs per Day
💰 $43.20 per Month
🟢 Pro Tip: Switching to LED grow lights reduces electricity costs by 50%+.
Who Should Use This?
This calculator is ideal for:
Small-scale home growers setting up their first tent
Experienced hobbyists testing new lighting setups
Gardeners upgrading from CFLs to LEDs or HPS
Anyone looking to optimize energy use and plant yield
It’s not just about light—it’s about using light wisely.
Final Tips Before You Start Growing
Keep a lux meter or PAR meter handy if you want to validate intensity readings.
Adjust hanging heights weekly during the flowering stretch.
Don’t forget to factor in reflective surfaces and canopy spread—they affect how evenly light hits the plants.
Whether you’re running a 2×2 micro grow or a 4×8 setup, this calculator helps you plan smart, grow better, and avoid costly mistakes.
FAQs – Grow Room Lighting, Ventilation & Cost Calculator
❓ How do I calculate the right grow light wattage?
Multiply your grow area by the recommended PPFD levels.
❓ How often should I exchange the air in my grow tent?
Every 1-3 minutes to keep conditions optimal.
❓ What’s the ideal CFM for a 4×4 grow tent?
200-250 CFM for proper ventilation.
❓ Does CO₂ supplementation increase plant yield?
Yes! It boosts growth by up to 30% when controlled properly.
Disclaimer for Grow Light Coverage , Ventilation & Electricity Cost Calculator
This Grow Room Lighting, Ventilation & Electricity Cost Calculator is for informational purposes only. Results are estimates and should not replace professional advice. Factors such as room conditions, light efficiency, and local electricity rates may affect actual performance. Always consult a grow expert or electrician before making changes to your setup.
Discover Crop & Farming Calculators