Cannabis Yield Calculator

How to Calculate Cannabis Yield

The most widely used method for estimating cannabis yield is the grams-per-watt (g/W) model. It works by multiplying total light wattage by an efficiency factor that reflects growing skill, environment, and genetics. A beginner with a 400 W light might harvest 200 g (0.5 g/W), while an expert could pull 480 g (1.2 g/W) from the same fixture.

Here is the step-by-step formula this calculator uses:

1. Total wattage — Multiply the true wall draw of each fixture by the number of lights. For example, 2 lights at 400 W = 800 W total.
2. Base yield — Multiply total wattage by the g/W efficiency factor for your experience level (Beginner 0.5, Intermediate 0.75, Advanced 1.0, Expert 1.2).
3. Medium modifier — Adjust by growing medium: Soil ×1.0, Coco Coir ×1.15, Hydroponics ×1.25, Living Soil ×0.95.
4. Strain modifier — Adjust by genetics: Indica ×1.0, Sativa ×0.9, Hybrid ×1.0, Autoflower ×0.7.
5. Yield range — The final estimate is shown as a range: result ×0.8 (conservative) to result ×1.15 (optimistic), accounting for environmental variance.

This model is an estimate. Real-world yields vary with temperature, humidity, CO₂ levels, training technique, and nutrient management. Use the result as a planning baseline and track actual harvests to refine your personal g/W benchmark over time.

Factors That Affect Cannabis Yield

Yield is not determined by a single variable. These six factors interact to set your harvest ceiling:

• Light intensity and spectrum — Light is the primary driver of photosynthesis and bud production. Modern full-spectrum LEDs produce 1.0 - 1.5 g/W, while traditional HPS fixtures typically deliver 0.5 - 1.0 g/W. Aim for 600 - 900 PPFD during flower (or up to 1200 PPFD with supplemental CO₂).
• Growing medium — Hydroponics gives roots unrestricted access to dissolved oxygen and nutrients, boosting growth rates 20 - 25 % over soil. Coco coir splits the difference, offering soil-like simplicity with hydro-like nutrient availability.
• Genetics — A strain's genetic ceiling determines maximum yield. Indica-dominant hybrids tend to produce dense, heavy colas, while pure sativas stretch tall and fill out more slowly. Autoflowers trade some yield for a faster, fixed-schedule life cycle.
• Plant training — Techniques such as Low-Stress Training (LST), topping, super-cropping, and SCROG create an even canopy where every bud site receives direct light. Trained plants routinely yield 20 - 40 % more than untrained ones.
• Environment — Temperature (24 - 28 °C in flower), relative humidity (40 - 50 % in late flower), and airflow all influence transpiration, nutrient uptake, and resin production. Dialing in VPD (vapor pressure deficit) alone can improve yields by 10 - 15 %.
• Nutrients — Proper macro- and micro-nutrient ratios prevent deficiencies that stunt growth. Overfeeding is equally harmful. Most high-yield growers follow a structured feed chart and monitor runoff EC/pH weekly.

Average Cannabis Yield by Growing Method

The table below compares typical yields across the most common cultivation approaches. Numbers assume a moderately experienced grower with adequate lighting.

How to Maximize Your Cannabis Yield

1. Use Low-Stress Training (LST) — Gently bend and tie branches outward to create a flat canopy. LST alone can boost yield by 20 - 30 % with zero extra equipment.
2. Top your plants — Remove the apical meristem at the 4th or 5th node. Each topped site becomes two main colas, adding 15 - 20 % more bud weight.
3. Install a SCROG net — A screen placed 20 - 30 cm above the canopy forces lateral growth and exposes more bud sites to direct light, improving yields by up to 30 %.
4. Optimize DLI (Daily Light Integral) — Target a DLI of 40 - 50 mol/m²/day during flower. Running lights at the right PPFD for 12 hours gets you there. Under-lighting by even 20 % directly translates to 20 % less flower weight.
5. Supplement CO₂ to 1200 - 1500 ppm — With high light intensity, supplemental CO₂ lets plants photosynthesize faster, boosting yields 20 - 30 % over ambient levels.
6. Dial in VPD — Keep vapor pressure deficit between 0.8 - 1.2 kPa during flower. Proper VPD maximizes transpiration and nutrient uptake without inviting mold.
7. Defoliate strategically — Remove large fan leaves that block bud sites at weeks 1 and 3 of flower. Light penetration to lower buds can increase total dry weight by 10 - 15 %.
8. Avoid nutrient burn in late flower — Reduce feed strength to 50 - 60 % in the final two weeks. Overfeeding late in flower does not add weight and can reduce bag appeal and flavor.