Calculating Microgreen Seed Density For Your Planting Trays

Calculating microgreen seed density might be the most challenging part of growing microgreens. 

Now, don’t get me wrong, you can throw any amount of seed on a soil medium and microgreens will grow.

So you have that going for you, but not having the correct microgreen seed density can cause problems.

how to calculate microgreen seed density

Remember, if you are using Home Microgreens planting trays the seed packets listed in the Store have the optimal number of seeds for those trays. 

If you’re using your trays, this article will explain how to calculate the number of Home Microgreen seed packets you need to grow perfect microgreens.


We’ve added a new calculator! BUT, this article still has a lot of great information that explains the Home Microgreen method so please read on. Below is a button that will take you to the new article.

Why Microgreen Seed Density is Important?

As I said, you can throw any amount of microgreen seed on a soil mix, and microgreens will grow.

So why is seeding density so important?

home microgreens sells seeds

FREE Home Microgreens Grow course that teaches you the basics of growing microgreens in your home! There are 12 video lessons (over 120 minutes), downloads, and more written information and tips!

I’ll write an article on this topic soon. But let me quickly touch on the reasons as I think it’s important to state why Home Microgreens takes the time to grow out microgreens and find the correct microgreen seed density.

If you want to skip down to the calculations click this link.

calculating microgreen seed density

Low & High Seed Density

Briefly, too low a seeding density wastes your time, electricity, and a lot of your soil volume. This isn’t efficient, and it costs you money.

Too high a seed density causes crowding when the plants grow, stunting them and giving you less plant mass than planting fewer seeds. The crowded young plants also won’t receive as much light causing them to be less nutritious.

Lastly, crowded plants cause poor air circulation increasing the risk of fungal disease.

We want to eat the healthiest microgreens possible, so we’re growing them at home in the first place. 

Planting at the correct seed density will optimize plant growth and produce nutritious microgreens.

Microgreen Seeds Come in Different Sizes and Densities

You can’t generalize and say a teaspoon or tablespoon of microgreens seeds is the perfect amount for a tray.

Seeds of microgreen varieties are of different sizes, so a set volume measure won’t produce the perfect density for all green. Seeds also have different densities—some, like cilantro, float, while others are dense enough to sink.

Therefore, you can’t use one weight measure or the mass of seed as a universal measure.

microgreen seed size

Microgreen seeds come in a wide range of sizes and densities.

Instead We Want the Same Number of Seeds per Square Inch

We’ve found that the number of seeds per square inch is a better way of determining how many seeds we want to plant on any particular tray. 

However, this doesn’t work for all seeds, especially the larger microgreen seeds. We test and retest microgreen plantings until we find the correct microgreen seed planting density for each variety.

Calculating Microgreen Seed Density For Your Own Planting Trays

As mentioned, Home Microgreen seed packets are pre-measured to be perfect for the Home Microgreen planting trays. 

Each tray has about 37.5 square inches of plantable surface area.

The Home Microgreen Store sells pre-measured seed packets for 10-inch by 10-inch trays, and you can buy seed by the gram for most varieties. 

Calculate the Area of Your Planting Tray

To calculate the area of your planting tray, measure the length and width of the tray in inches. If the tray is oval or some other odd shape, estimate what the rectangular size would be. 

Enter the length and width of your planting tray in the form below, and it will calculate the area of your planting tray in square inches.

The form will also calculate the number of Home Microgreen Pre-measured Seed Packets you need for the perfect microgreen seed density for your planting tray.

Calculating How Many Grams of Microgreen Seed You Need

If you want to know how many grams of a particular microgreen seed you need for your planting tray, the form below will calculate it for you. 

Data for the form will come from the output box of the previous form and information from the Home Microgreens Store. 

Enter the number of Home Microgreen seed packets from the previous form into the first input box.

Use the button and go to Home Microgreens Store and search for the microgreen variety you are interested in growing.

The description’s first sentence will list how many grams of seed are in a package. 

Enter that number into the second input box. 

The form will calculate how many grams of seed you need for the perfect microgreen seed density for your planting tray. 

The Best Way to Calculate Microgreen Seed Density

A general rule using a set volume or weight of seeds for all microgreen varieties doesn’t work because each type of microgreen has a seed of different size or density.

The best way is to use a set number of seeds per square inch of growing area. Luckily, many growers publish the approximate number of seeds per unit of mass.

Knowing the area of a planting tray and the number of seeds in a given mass, we can guesstimate the weight in grams we need for each tray.

However, this isn’t the end. It’s only a starting point.  

We grew each microgreen type several times and tracked how much seed we planted (mass). When the greens matured, we weighed the harvest and observed the condition of the plants. 

We found the optimal seed mass to use with our 38 square-inch trays from those data. Then all we have to do is set up ratios to calculate the mass of seed needed for any other size tray. 

Although we use a seed mass at the end to seed microgreen trays, the mass was determined based on a set amount of seeds per square inch and optimized by running trials.

Our method is one of the best to calculate the mass of seeds needed for any particular microgreen planting tray. 

Give it a try and see.

Once you’ve tried the method, comment below and let us know how it went. In the meantime, we will be tweaking and improving our formulas for the home microgreen grower.

We’ve Made It Easier!

We’ve added a Microgreen Seed Calculator!

Use the button below to check out the new article and updated calculator.

Have a Question About This Article?

If you have any questions about the information in this post or microgreens in general, please comment below or contact me using the Ask a Question page


  • Todd

    Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including MyViewFromTheWoods.com. Todd worked at a large farm market, garden & nursery center for 20 years. Somehow he snuck off to become a geologist and professor before coming back to his senses to write & lecture about microgreens and gardening. When not at the computer, he can be found in the garden, trout stream, or mountain trail with his new Springer Spaniel Caden.

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