Read the expanded yield
Compressed and hydrated coir describe different states. Find the stated expanded volume for the specific product. A supplier may give a range; do not assume every brick of the same weight produces the same usable volume. Use consistent volume units throughout the purchase.
Calculate the coir portion
If your selected recipe needs 3 cubic feet of final mix and specifies 40% coir by volume, the coir portion is 1.2 cubic feet. The percentage is an arithmetic example, not a universal growing recipe. Calculate the other ingredients separately from their own volume shares.
Round up whole blocks
Suppose your particular block is labelled to yield at least 0.5 cubic feet when expanded. A 1.2 cubic foot target needs 1.2 ÷ 0.5 = 2.4 blocks, so buy three. Their minimum stated yield is 1.5 cubic feet. These hypothetical figures demonstrate the method, not a brand specification.
Use the bag calculator for blocks
Enter your coir target and the expanded yield per block as the unit capacity. The result labelled bags represents blocks for this calculation. Use the price per block; for a multi-block pack, either divide its price or use the total pack yield consistently.
Follow hydration instructions
Hydrate according to the manufacturer’s directions and check the prepared material before allocating it to pots. Do not add the water volume to the expanded yield as extra growing medium. Weight-to-volume shortcuts are unreliable across products. If a yield is a range, plan using its lower end.
Frequently asked questions
Can I calculate from brick weight alone?
Not without a product-specific expanded yield.
Do I add hydration water to the yield?
No. Use the declared final expanded volume.