Why Predict Mushroom Yield?

Small-scale mushroom cultivation is growing in popularity among home gardeners and urban farmers. Knowing roughly how many mushrooms you will harvest helps plan meals, farmers market sales, or upcoming experiments with new strains. Yields depend on many factors, including the type of mushroom, the quality of your spawn, and how carefully you control moisture and temperature. This calculator offers a simple approximation using a yield ratio—the proportion of fresh mushrooms obtained from the weight of colonized substrate.

Understanding the Formula

A common rule of thumb for oyster mushrooms is that one kilogram of spawn mixed with 5–6 kilograms of hydrated substrate produces approximately 25% of that combined weight in fresh mushrooms. The generalized MathML equation for estimating yield is:

where $r$ is the expected yield ratio, $\mathrm{S\_w}$ is spawn weight in kilograms, and $\mathrm{S\_v}$ is substrate volume converted to kilograms (a liter of hydrated straw roughly equals one kilogram). The result estimates total harvest weight in kilograms.

Making the Most of Your Grow

This calculation assumes optimal conditions. Cleanliness, consistent humidity, and proper air exchange are crucial for strong yields. If you use hardwood sawdust or other dense substrates, convert volume to weight to maintain accuracy. Some growers see ratios up to 50%, while others may get less than 20% depending on strain and environmental control. Use this number as a baseline and adjust with experience.

Tracking each batch in a notebook can help refine your expectations. Record how much spawn and substrate you used, along with final harvest amounts. Over time, you’ll learn the best ratios and conditions for your space, making each crop more reliable and profitable.