Free calculators for mulch, compost, soil and raised beds (I made them, no sign-up)

I built a set of free garden calculators and thought they might save some of you the back-of-envelope maths. No sign-up, no app, works on a phone in the garden.

Mulch: enter the area and depth, get the volume and number of bags. Example: 10 m² at 7.5 cm deep is 0.75 m³, about 13 bags of 60 L.
Mulch depth and volume calculator

Raised beds: fill volume, plus a guide on layering. Example: a 120 × 240 cm bed filled 30 cm deep takes 864 L.
Raised bed soil calculator · How to fill a raised bed

Compost: how much to spread, or how much a bin holds.
Compost volume calculator

Plant spacing: how many plants fit a bed at a given spacing.
Plant spacing and plant count

Full disclosure: it's my site and it carries ads, which is how it stays free. If a number looks off for your situation, or there's a calculator you'd find useful, tell me here and I'll fix or add it.

Sam