# Bread scale

The unit of value in OpenYield is **Bread** (REQ-013). Bread is scaled in 11
tiers, each 1,000× the previous, so a Holder can reason about a Crumb and a
Granary in the same mental model:

| Tier | Name | Multiple |
|---|---|---|
| 1 | **Grain** | 1 |
| 2 | **Crumb** | 1,000 Grain |
| 3 | **Bread** | 1,000 Crumb |
| 4 | **Loaf** | 1,000 Bread |
| 5 | **Batch** | 1,000 Loaf |
| 6 | **Cake** | 1,000 Batch |
| 7 | **Bakery** | 1,000 Cake |
| 8 | **Granary** | 1,000 Bakery |
| 9 | **Mill** | 1,000 Granary |
| 10 | **Harvest** | 1,000 Mill |
| 11 | **Earth** | 1,000 Harvest |

## Why 11 tiers

The 11-tier scale gives the mesh a single unit for everything from a
1-Grain internal minimum (the Fee Covenant floor) to the Earth-tier totals
held in the Root-Pool. There is no separate "small unit" and "large unit":
the Bread scale is the unit. The 1-Grain minimum prevents dust games; the
tier names keep human-readable values at every scale.

## Where Bread lives

Bread is held in the three [Storage Pools](storage-pools.md): the Stash
(Holder-level), the Vault (Stand-level), and the Root-Pool (treasury). The
Watchers attest to the state of the pools daily; the Mirror mirrors the
canonical state to the bearers. See [Watchers & Mirror](watchers-mirror.md)
for the attestation layer.