The same 1.62 cubic meters, two different answers
A 1.8m × 1.8m area poured 0.5m thick comes out to exactly 1.62 cubic meters — the same volume as 6 columns measuring 0.3m × 0.3m × 3m each. The raw volume calculator gives exactly one number for this: 1.62 m³. On its own, that number is sufficient to order 1.62 m³ of ready-mix concrete from a supplier.
What's missing for a materials order
Ordering cement, sand, and aggregate separately needs two things the raw volume alone doesn't provide: a mix ratio (what fraction of the mix is cement versus sand versus aggregate) and a dry-volume adjustment, since loose dry materials take up more space than the same mix does once wet and compacted.
Applying both to the same 1.62 m³
Using an M20 mix ratio (1:1.5:3) with a 5% wastage allowance, that 1.62 m³ of wet concrete becomes 13.7 cement bags, 0.714 m³ of sand, and 1.429 m³ of aggregate — three separate purchase quantities derived from the one starting volume, none of which the raw volume figure alone would have revealed.
When each calculator is the right tool
The plain volume calculator is the right tool when ready-mix concrete will be ordered directly by the cubic meter. The column and footing calculators (or any other material-breakdown calculator) are the right tool when the concrete will be mixed on-site from raw cement, sand, and aggregate — the same underlying volume, answering two different practical questions.