This peat soil mix calculator helps gardeners who still use peat mixes and want the right parts turn a soil guess into a clear plan. You enter a few numbers, and the tool works out the amounts for you. That matters because soil is the one garden input you cannot fix in a day: too little organic matter and plants starve, too much of one amendment and the mix goes wrong for a whole season. A written plan keeps each bed balanced, so plants grow without stress.
Peat has been the classic base for potting mixes for decades, because it holds water, stays light, and is almost free of weed seeds. Seedlings love it for exactly those reasons. But peat comes from bogs that took thousands of years to form, and digging them releases stored carbon and destroys wildlife habitat. That is why many gardeners now use peat only for seeds, or switch to coir and compost mixes for everything else. If you do use peat, use it well and waste none of it.
To use the tool, enter each value in order: Number of pots, Pot volume in litres, Peat share in percent. Then press Calculate to see the result. Each line shows one part of the plan, so you can spot a number that looks wrong before you carry a bag outside. If you change any value, press Calculate again. The example button fills in a worked case so you can see how the tool behaves before you enter your own numbers.
Here is a worked example. Take 5 pots of 8 litres each with a 60 percent peat share need 40 litres of mix in total, made of 24 litres of peat, 8 litres of perlite and 8 litres of compost. That result is the point of the tool: one clear plan, with each part visible. If a neighbour asks why you mixed the soil that way, you can walk through the same lines. If your bed is bigger or smaller, you change one number and the plan updates. That makes changes fast and keeps the garden honest about what each bed really needs.
Peat mixes are at their best for spring seed sowing, when steady moisture matters most. Wet peat fully before you sow: dry peat repels water, and a tray that looks watered can still be dry inside. In summer, peat pots dry fast at the edges, so check daily and water before the mix pulls away from the pot. At the end of the season, tip used peat mix onto beds as a soil improver instead of throwing it away.
Three mistakes show up again and again. The first is watering dry peat from above and assuming it soaked in, when water ran straight down the sides. The second is using peat alone with no perlite, so the mix compacts into a wet brick. The third is buying peat for every job, when compost mixes would do the same work with less harm. Soak it, open it with perlite, and save peat for seeds.
Tips
- Test a small patch first. One pot or one corner tells you more than a whole bed mixed on a guess.
- Add organic matter every season. Soil life eats compost, so a bed fed once slowly goes hungry again.
- Mulch every bed. Bare soil dries fast, while mulched soil holds water for days longer.
How do I know if my soil improved?
Squeeze a handful of damp soil: good soil crumbles softly instead of sticking in a lump or falling to dust. Also watch drainage after rain and how long beds stay moist in a dry week.
Can I mix too much of an amendment?
Yes. Most amendments help in a modest share and hurt in excess, so follow the tool result and mix evenly rather than tipping in a whole bag at once.
How often should I re-test or re-plan?
Once a season is enough for most beds. Re-plan after a wet winter, after adding a large amount of compost, or when a bed starts behaving differently from its neighbours.
Versión en español: Calculadora de Mezcla de Suelo con Turba