Houseplant Light Requirement Calculator

How to Use the Houseplant Light Requirement Calculator

This calculator helps you match your houseplants to the best window or location in your home based on two simple inputs: the plant’s light preference and the direction your window faces. It is designed for beginners and plant enthusiasts who want a quick, practical guide rather than complex light measurements.

To use the tool, choose the light category that best fits your plant (low, medium, or high light), then select the window direction (north, east, south, or west). The calculator will suggest whether that spot is suitable, borderline, or unsuitable, and whether you might need to filter strong light or supplement weak light with a grow lamp.

Why Light Matters for Houseplants

Light powers photosynthesis, the process plants use to turn light energy into sugars and chemical energy for growth, leaf production, and flowering. Indoors, the amount and quality of natural light can vary a lot between different rooms and windows. Getting this wrong is one of the most common reasons houseplants struggle.

Too little light can cause:

• Slow or no new growth
• Leggy, stretched stems reaching toward the window
• Pale or yellowing leaves
• Failure to flower in blooming species

Too much light can lead to:

• Brown, crispy patches on leaves (leaf scorch)
• Bleached or faded leaf color
• Dry, stressed soil even with regular watering

The calculator gives you a starting point, but always watch how your plant responds and adjust placement as needed.

Understanding Plant Light Categories

Most houseplants sold as indoor plants can be grouped into three broad light categories. These categories match the options you see in the calculator.

Low light plants

Low light does not mean no light. It means the plant can tolerate dimmer spaces away from a bright window. Typical examples include:

• Snake plant (Sansevieria)
• Pothos (Epipremnum aureum)
• ZZ plant (Zamioculcas zamiifolia)
• Cast iron plant (Aspidistra)

These plants often do well near north-facing windows or several feet back from a brighter window.

Medium light plants

Medium light plants prefer bright, indirect light. They like a well-lit room but usually need protection from harsh midday sun. Examples include:

• Peace lily (Spathiphyllum)
• Many ferns
• Philodendrons and many vining aroids
• Spider plant (Chlorophytum comosum)

They often thrive near east-facing windows or a few feet back from a south or west window where light is filtered by curtains or blinds.

High light plants

High light plants want lots of bright light, often with some direct sun for part of the day. Long-term deep shade will usually weaken them. Examples include:

• Succulents and cacti
• Fiddle-leaf fig (Ficus lyrata)
• Rubber plant (Ficus elastica)
• Many flowering houseplants like geraniums indoors

These plants usually do best right in a bright window, especially south- or west-facing in the northern hemisphere, or under strong grow lights.

How Window Direction Affects Light

The direction your window faces changes both the intensity and timing of sunlight entering your home. The calculator uses these general patterns for the northern hemisphere:

• North-facing: Least direct sun, soft and consistent light. Best for low-light plants or medium-light plants placed close to the glass.
• East-facing: Gentle morning sun, bright but usually not too intense. Good for medium-light plants and many high-light plants that dislike harsh afternoon sun.
• South-facing: Longest duration of light and the strongest sun in winter. Excellent for high-light plants; medium-light plants may need sheer curtains.
• West-facing: Strong afternoon and early evening sun, which can be intense in summer. Suitable for high-light plants; medium-light plants may require some filtering.

Within each room, light intensity drops quickly as you move away from the window. As a rough guide, every step you take back from the glass significantly reduces the light your plant receives, even if the room still looks bright to your eyes.

Basic Light Level Relationship

At a simple level, you can think of a plant’s growth as increasing with available light up to a point, and then leveling off or declining if light is excessive. A very simple conceptual relationship is:

where G is growth and L is available light. In this calculator, rather than measuring light precisely, we group typical indoor situations into low, medium, and high ranges and match them to plant preferences.

Houseplant Light Levels by Window Direction

The table below summarizes how common window directions interact with plant light categories. Use it alongside the calculator results to fine-tune where you place each plant.

Interpreting Your Calculator Results

After you select a plant light category and window direction, the calculator evaluates how well they match and returns a recommendation. In general, you can expect three kinds of outcomes:

• Good match: The plant should do well in this spot with routine care. You may only need occasional adjustments like rotating the pot for even growth.
• Borderline match: The plant may survive but grow slowly, stretch, or show stress over time. Consider moving it closer to or farther from the window, or using sheer curtains.
• Poor match: The light level is likely too low or too intense for long-term health. In this case, the tool may suggest supplemental grow lighting or a different window direction.

Use the result as a guide, then observe your plant for several weeks. If you see signs of stress that do not improve with small adjustments, choose a more suitable spot following the categories above.

Worked Example: Placing a Fiddle-Leaf Fig

Imagine you brought home a fiddle-leaf fig, a popular but sometimes fussy high-light plant.

1. In the calculator, choose High Light under plant type.
2. Select your window direction. Suppose your brightest window faces West.
3. Submit the form to see the recommendation.

The calculator is likely to rate this as a good match but may warn about intense summer afternoon sun. Practical steps you could take include:

• Placing the plant a short distance back from the window to soften direct rays.
• Using a sheer curtain during the hottest months.
• Rotating the plant every few weeks for even growth.

If instead you choose North as the window direction, the calculator will probably flag this as a poor match or borderline spot. It may suggest adding a strong grow light above the plant or moving the fig to a brighter south or west window.

Common Signs Your Plant Has the Wrong Light

Signs of too little light

• New stems are long, thin, and weak (leggy growth).
• Leaves are smaller than usual or spaced far apart on the stem.
• Variegated leaves lose their variegation and turn mostly green.
• Soil stays wet for a long time because the plant is not using much water.

Signs of too much light

• Brown or crispy patches on the sides or tips of leaves.
• Bleached or faded areas where sun hits directly.
• Very dry soil and drooping leaves even with regular watering.

If the calculator suggests your window is slightly too bright, try moving the plant a bit farther from the window or adding a sheer curtain. If it suggests the spot is too dim, move the plant closer to the window, choose a brighter room, or add supplemental lighting.

Supplemental Lighting Options

Not every home has a perfect south-facing window. Grow lights can bridge the gap, especially for high-light plants in darker rooms.

• LED grow lights: Efficient, cool-running, and available in full-spectrum options that mimic daylight.
• Fluorescent lights: Useful for low- to medium-light plants, often in the form of tubes or compact bulbs.
• Placement: Many houseplants do well with the light positioned 6–12 inches above the foliage.
• Duration: Running lights for about 12–14 hours per day often mimics a natural day length.

When the calculator advises supplemental lighting, start with a modest setup and adjust based on plant response rather than aiming for a precise lux or foot-candle number.

Frequently Asked Questions

Can I keep high-light plants in a north-facing room?

Sometimes. If the room has large, unobstructed windows and very bright ambient light, a high-light plant placed right at the window or under grow lights can still thrive. In most typical homes, however, high-light species do better in east, south, or west windows or with added artificial light.

How far from the window should I place my plant?

As a general rule:

• High-light plants: within about 0–2 feet of a bright window.
• Medium-light plants: around 2–6 feet from a bright window, or right next to an east window.
• Low-light plants: 4 or more feet away from a bright window or in a room with indirect light for most of the day.

Use these ranges as starting points and adjust after watching how your plant behaves.

What is the difference between direct, indirect, and filtered light?

• Direct light: Sunbeams fall directly on the leaves, often near a south or west window.
• Bright indirect light: The room is well lit, but the plant is not in the sunbeam itself, or the light is softened by curtains.
• Filtered light: Light passes through sheer curtains, blinds, frosted glass, or foliage from outdoor trees before reaching the plant.

Assumptions and Limitations

The recommendations from this calculator are approximate and based on common indoor conditions. Keep these assumptions and limitations in mind:

• Hemisphere: The guidance assumes you are in the northern hemisphere, where south-facing windows receive the most sun. If you are in the southern hemisphere, the roles of north and south are broadly reversed.
• Typical windows: The tool assumes average-sized residential windows without heavy tinting. Very small windows or strongly tinted glass will reduce light; large floor-to-ceiling windows will increase it.
• Obstructions: Nearby trees, balconies, neighboring buildings, and deep window recesses can significantly reduce light, especially on lower floors.
• Seasonal changes: Sun angle and day length change with the seasons, so a spot that works well in summer may be too dim in winter, and vice versa.
• Plant variation: Each species, and even individual plants, can differ. The low/medium/high light categories are broad and do not replace detailed care guides for specific plants.
• No exact measurements: The calculator does not measure lux or foot-candles. It provides general guidance, not a guarantee of performance.

Always treat the output as a helpful starting point. Combine it with your own observations and, when needed, more detailed care information for your particular species.

Next Steps and Related Care Tips

Once you have found a promising spot using the Houseplant Light Requirement Calculator, monitor your plant over the next few weeks and adjust gradually. If your plant still struggles after light adjustments, factors like watering, soil, humidity, or pot size may be involved.

For more in-depth guidance, consider checking resources such as a general indoor plant care guide or a watering schedule calculator, if available on your favorite plant care sites. These can complement your light adjustments and help you create a balanced environment where your plants can truly thrive.