Ten ounces off one tray. What did each one cost?
Seed by the gram, soil, tray wear and your weighed harvest into a cost per tray and a cost per ounce — then the clamshell math that says whether your $5 price actually holds. Everything stays in your browser.
The tray
The harvest
The standing order
The numbers here are yours to check. This page does arithmetic on what you type — it cannot see your recipe, your equipment or your batch.
For anything you will eat or sell as food, double-check it against your own process and your local rules. This page does maths, not food safety.
Want it to remember?
In MadeKeeper the same math stops being a one-off: seed grams and soil are consumed the day you seed, clamshells at pack-out, and your real logged yields quietly replace these seeded defaults tray after tray, so the cost per ounce in your ledger is yours — not an example's. See for growers or poke around the live demo. $19/mo for the whole back office, kept for as long as you stay. The shop stays free for cost a piece and one fair — no product cap. The tax packet, Etsy and Square, and more fairs are the $19.
Free tool — no signup
The numbers microgreens growers actually argue about — seeding charts, tray life, and the light bill — and where each one is a setting you own, not a constant we picked for you.
What does a tray of sunflower shoots actually cost?
Run the example numbers: 100 g of seed at $9 a pound is $1.98 (grams ÷ 453.6 × your price per pound), call it 60¢ of soil, and a $4 tray spread over 10 uses adds 40¢ — $2.98 for the tray. Cut and weigh 10 oz off it and you're at just under 30 cents an ounce. If you haven't weighed a harvest yet, the cost-per-tray answer still stands on its own; the per-ounce number waits for your scale, because your weighed yield is the spine everything downstream hangs from.
Why do I have to enter my own seed weight instead of picking a crop from a chart?
Because the published charts don't agree: put two suppliers' seeding recommendations for the same crop side by side and they can land surprisingly far apart, and whether you soak changes the picture again. That's not a gap a calculator should paper over by quietly picking a side, so grams per tray is a setting you own — enter what you actually sow. It's also the one number this tool refuses to guess: with no seed weight there's no honest cost per tray, just somebody else's.
How many uses should I spread a tray's price across?
This is the argument that never ends — some growers retire a 1020 after 10 rounds, others swear theirs are still square at 50. The default here is 10, deliberately conservative: a $4 tray adds 40¢ per crop at 10 uses, versus the 8¢ a 50-use assumption would give you. It's a setting rather than a verdict because tray life depends on how you wash, stack and handle yours — change it once to your real count and the amortization follows everywhere.
Do my $5 clamshells actually make money — and does the light bill count?
Take the sunflower example: at just under 30¢ an ounce, a 2 oz fill is about 60¢, a shell adds 25¢, and the clamshell costs roughly 85¢ — so a $5 price leaves a little over $4 before the booth fee and your time. Swap in your own crop, price and weighed yield and the same math answers for pea shoots or radish, straight off your scale. Lights and electricity stay out by default, because growers genuinely split on whether power belongs in each tray's true cost or in general overhead — if you want it in, flip the toggle and add your cents per tray.