A window light estimator calculates estimated foot-candles in your room based on window direction, size, distance, and obstructions. Light intensity is the most important factor in houseplant placement — this tool takes the guesswork out of matching plants to your actual light conditions.
Window Details
Set your window details and click Estimate Light Level to see foot-candles and plant recommendations.
Estimates are based on typical conditions for the northern hemisphere. Actual readings vary by season, latitude, and local weather. For precision, use a light meter app. Foot-candle values shown represent a midday average on a clear day.
How to Use the Window Light Estimator
The window light estimator helps you determine how many foot-candles your houseplants receive at a specific spot in your home — without needing a light meter. Simply enter your window's facing direction, size, your distance from the window, and any outside obstructions, and the tool calculates an estimated foot-candle range with a list of suitable plants.
Step 1: Select Your Window Direction
Click the compass rose to indicate which direction your window faces. South-facing windows receive the most light year-round in the northern hemisphere (700–900 fc on clear days). East windows get bright morning sun (400–600 fc). West windows get afternoon sun at similar levels. North windows receive consistent but low ambient light (75–150 fc). Diagonal directions (NE, SW, etc.) fall between their cardinal neighbors.
Step 2: Enter Window Size and Distance
Larger windows let in more total light, which matters for plants positioned off to the side. Enter the window width and height in feet (or meters with the metric toggle). Then enter the distance from the window to where your plant sits. Light drops off quickly with distance — a plant at 6 feet from a south window may only receive 25% of the light available at the glass.
Step 3: Set Obstruction Level and Floor
Select whether trees, buildings, or overhangs block some of your window's sky view. A dense tree right outside a window can halve the effective light. Higher floors tend to receive more light because nearby buildings and trees obstruct less of the sky angle. The tool applies appropriate multipliers for each combination.
Step 4: Read the Results
The output shows an estimated foot-candle range, a light level category (low, medium, bright indirect, or direct), and a list of houseplants from our 100-plant database whose ideal light range overlaps with your estimate. Use these suggestions as a starting point — observe your plants over a few weeks and adjust if they show signs of too much or too little light.
Light Level Quick Reference
Low light (under 100 fc): North windows, far from windows, rooms with small windows. Pothos, snake plants, ZZ plants, cast iron plants.
Medium light (100–300 fc): East windows, several feet from south/west windows. Peace lilies, dracaenas, Chinese evergreens.
Bright indirect (300–1,000 fc): East windows at close range, south/west windows set back. Monsteras, fiddle leaf figs, palms, bird of paradise.
Direct light (1,000+ fc): Right at a south or west window with no obstructions. Succulents, cacti, herbs, citrus trees.
FAQ
Is this window light estimator free?
Yes, the window light estimator is completely free with no signup required. Enter your window details and instantly see estimated foot-candles and suitable plant suggestions. Everything runs in your browser.
Is my data private?
Absolutely. All calculations happen locally in your browser. No data is sent to any server. Your window details and plant preferences stay completely private on your device.
What are foot-candles and why do they matter for plants?
Foot-candles (fc) measure the intensity of light hitting a surface. One foot-candle equals the light from one candle at one foot away. Plants need different amounts: low-light plants thrive at 25-100 fc, medium-light at 100-300 fc, bright indirect light at 300-1000 fc, and direct sun lovers at 1000+ fc.
Which window direction gives the most light for houseplants?
South-facing windows receive the most light in the northern hemisphere, providing 800+ foot-candles on sunny days. East and west windows offer moderate bright indirect light (300-600 fc). North-facing windows receive the least light (100-200 fc) and are best for low-light plants like pothos and ZZ plants.
How does distance from the window affect light levels?
Light intensity drops significantly with distance. At 1 foot from a south window you might have 800 fc, but at 5 feet it drops to roughly 250 fc, and at 10 feet to around 100 fc. The tool uses an inverse distance formula to estimate this attenuation based on your input.
How do obstructions like trees affect plant light?
Partial obstructions (trees, nearby buildings) can cut light by 50%, reducing a bright south window to medium-light levels. Heavy obstructions like deep overhangs or very close buildings can reduce light by 75%, which is why outdoor context matters as much as window direction.
Should I use metric or imperial measurements?
Use whichever system you prefer. Toggle between feet/inches and meters using the unit switch. The foot-candle output remains the same regardless of which unit system you use for measurements.
How accurate are these foot-candle estimates?
The estimates are approximations based on directional light research and distance physics. Real-world readings vary by season, cloud cover, latitude, and exact window geometry. For precision growing, use a light meter app or dedicated PAR meter. This tool gives a reliable ballpark for plant selection decisions.