Seed Tray Count
Calculator

It divides the total number of seedlings you want to start by the number of cells per tray (commonly 72, 128, or 200 cells depending on cell size), rounding up to the next whole tray since partial trays still take up the same growing space.

Larger cells hold more soil and support stronger root development before transplanting, which matters for slower-growing or larger seedlings like tomatoes, while small cells (200+ per tray) work fine for quick, small-rooted crops like lettuce or herbs that transplant sooner.

Yes, factor in your seed's expected germination rate (often 70-90% depending on species and seed age) by starting slightly more cells than your final target plant count, or plan to sow two seeds per cell and thin to one after germination.

It can, since sowing two seeds per cell and thinning to the stronger seedling after germination often produces the plant count you need from fewer total cells than sowing one seed per cell and hoping for a high germination rate.

Small cells that work for germination become root-bound within a few weeks as the seedling's root system outgrows the available soil volume, which stresses the plant, so seedlings are typically potted up to larger containers before their final transplant outdoors.