Methodology
Calculated vs. purchase
Every material shows two numbers. Calculated is the exact math for your project's geometry, before any purchase adjustment. Purchase is what to actually buy — it adds the waste or ordering allowance for that layer, then applies the rule below depending on how the material is sold.
Discrete vs. bulk materials
Pavers, bags, and edge restraint pieces are always rounded up — they're sold as whole units. Base gravel and bedding sand are sold by weight or volume in continuous amounts, so we show the calculated figure without inventing a rounding rule your supplier may not use.
Where the numbers come from
Where a manufacturer spec sheet or technical standard gives us a real number, we cite it. Where no universal standard exists — like waste percentage by laying pattern, or edge restraint spike spacing — we say so explicitly and use a conservative planning estimate you can override.
Advisory notes
Some notes don't block your calculation — they're practical heads-up, like a minimum joint depth some polymeric sand products require, or compacting deep gravel in layers rather than all at once.