以下详细说明暂以英文提供。
How deep should new topsoil be?
Four inches over an existing lawn is the classic recipe for leveling and refreshing grass — deep enough to feed roots, shallow enough not to smother them. Patchy or clay-heavy ground benefits from six inches of good loam, while raised vegetable beds want eight to twelve. Whatever the target, loose delivery settles, so the spread height shrinks by about a quarter over the first few weeks of rain and foot traffic.
Yards, tons, and the bag question
Suppliers sell by the cubic yard; some quote weight, which lands near 1.25 tons per yard for loose screened soil. Bags are the other route: a 40-pound bag holds roughly 0.375 cubic feet, so a single cubic yard is about 72 of them. That arithmetic settles the bags-versus-bulk debate fast — bags make sense for a bare patch or a small bed, and anything past twenty or thirty of them is cheaper, cleaner, and far easier on your back as a bulk delivery.
中国本地参考
日常计算时值得知道的中国本地规则：
- 计量的单位习惯: 住房面积用平方米，土地常用亩（1 亩 ≈ 666.7 平方米）；里程用公里，油耗用 L/100km。
- 日期与数字格式: 日期写作 2026年10月13日（年-月-日）；大数习惯用万、亿（1 万 = 10,000，1 亿 = 100,000,000）。
- 法定节假日: 全年法定节假日 11 天，春节与国庆为长假；调休安排每年由国务院办公厅发布。
- 速度与限速: 高速公路最高限速 120 km/h，城市快速路多为 80 km/h，均以公里每小时计。
- 鞋服尺码: 鞋码用中国码（毫米制），服装常用 155/80A 这类身高围度组合，与欧美码不同。
数据核对：2026 年 10 月
常见问题
How much area does one cubic yard cover?
At a 4-inch depth, one yard spreads across about 80 square feet — a 9×9 patch. At 6 inches it covers roughly 54 square feet, and at 2 inches closer to 160.
Can I put topsoil straight over grass?
Up to about 2 inches, yes — the grass grows through. Deeper than that, remove the sod or till first, or the old lawn becomes a buried thatch layer that sheds water and roots.
Is screened topsoil worth it?
For lawns and beds, usually yes: screening removes rocks and clods so the soil spreads evenly and rakes flat. Fill-dirt-grade soil is fine for leveling subgrade, but put the screened material on top where the roots live.