diff --git a/cista/protocol.py b/cista/protocol.py
index 7ebd221..c04147a 100644
--- a/cista/protocol.py
+++ b/cista/protocol.py
@@ -146,6 +146,7 @@ class FileEntry(msgspec.Struct, array_like=True, frozen=True):
     key: str
     mtime: int
     size: int
+    allocated: int
     isfile: int
 
     def __str__(self):
@@ -177,5 +178,6 @@ class UpdateMessage(msgspec.Struct):
 class Space(msgspec.Struct):
     disk: int
     free: int
-    usage: int
+    used: int
     storage: int
+    allocated: int
diff --git a/cista/watching.py b/cista/watching.py
index 9bdef50..b7456b5 100644
--- a/cista/watching.py
+++ b/cista/watching.py
@@ -24,7 +24,7 @@ sortkey = natsort_keygen(alg=ns.LOCALE)
 class State:
     def __init__(self):
         self.lock = threading.RLock()
-        self._space = Space(0, 0, 0, 0)
+        self._space = Space(0, 0, 0, 0, 0)
         self.root: list[FileEntry] = []
 
     @property
@@ -148,12 +148,15 @@ def walk(rel: PurePosixPath, stat: stat_result | None = None) -> list[FileEntry]
     try:
         st = stat or path.stat()
         isfile = int(not S_ISDIR(st.st_mode))
+        # st_blocks is in 512-byte units
+        allocated = st.st_blocks * 512 if isfile else 0
         entry = FileEntry(
             level=len(rel.parts),
             name=rel.name,
             key=fuid(st),
             mtime=int(st.st_mtime),
             size=st.st_size if isfile else 0,
+            allocated=allocated,
             isfile=isfile,
         )
         if isfile:
@@ -181,8 +184,9 @@ def walk(rel: PurePosixPath, stat: stat_result | None = None) -> list[FileEntry]
                 level=entry.level,
                 name=entry.name,
                 key=entry.key,
-                size=entry.size + child.size,
                 mtime=max(entry.mtime, child.mtime),
+                size=entry.size + child.size,
+                allocated=entry.allocated + child.allocated,
                 isfile=entry.isfile,
             )
             ret.extend(sub)
@@ -227,7 +231,14 @@ def update_path(rootmod: list[FileEntry], relpath: PurePosixPath, loop):
 def update_space(loop):
     """Called periodically to update the disk usage."""
     du = shutil.disk_usage(rootpath)
-    space = Space(*du, storage=state.root[0].size)
+    root = state.root[0]
+    space = Space(
+        disk=du.total,
+        free=du.free,
+        used=du.used,
+        storage=root.size,
+        allocated=root.allocated,
+    )
     # Update only on difference above 1 MB
     tol = 10**6
     old = msgspec.structs.astuple(state.space)
@@ -504,8 +515,66 @@ class PathIndex:
 
         self.root = new_root
         self._rebuild()
+
+        # Recalculate sizes for ancestor folders (including root)
+        self._recalculate_ancestors(path)
+
         return new_root
 
+    def _recalculate_ancestors(self, path: PurePosixPath):
+        """Recalculate size/allocated for all ancestors of path, including root."""
+        # Build list of ancestors from deepest to root
+        ancestors = []
+        current = path.parent if path.parts else PurePosixPath()
+        while True:
+            ancestors.append(current)
+            if not current.parts:
+                break
+            current = current.parent
+
+        # Process from deepest ancestor to root
+        for ancestor_path in ancestors:
+            if ancestor_path not in self._index:
+                continue
+            start, count = self._index[ancestor_path]
+            if count == 0:
+                continue
+
+            ancestor = self.root[start]
+            if ancestor.isfile:
+                continue  # Files don't aggregate
+
+            # Sum size/allocated of direct children
+            total_size = 0
+            total_allocated = 0
+            i = start + 1
+            while i < start + count:
+                child = self.root[i]
+                if child.level == ancestor.level + 1:
+                    total_size += child.size
+                    total_allocated += child.allocated
+                    # Skip child's subtree
+                    child_path = ancestor_path / child.name
+                    if child_path in self._index:
+                        _, child_count = self._index[child_path]
+                        i += child_count
+                    else:
+                        i += 1
+                else:
+                    i += 1
+
+            # Update ancestor entry if changed
+            if ancestor.size != total_size or ancestor.allocated != total_allocated:
+                self.root[start] = FileEntry(
+                    level=ancestor.level,
+                    name=ancestor.name,
+                    key=ancestor.key,
+                    mtime=ancestor.mtime,
+                    size=total_size,
+                    allocated=total_allocated,
+                    isfile=ancestor.isfile,
+                )
+
 
 def collapse_paths(paths: set[PurePosixPath]) -> set[PurePosixPath]:
     """Remove child paths if parent is in set."""
diff --git a/frontend/src/components/DiskSpace.vue b/frontend/src/components/DiskSpace.vue
index 429aa8a..8134db0 100644
--- a/frontend/src/components/DiskSpace.vue
+++ b/frontend/src/components/DiskSpace.vue
@@ -36,9 +36,9 @@
       </g>
 
       <g ref="labelsRef" class="pie-labels">
-        <text :x="storageInnerPos.x" :y="storageInnerPos.y" class="pie-label-inner" :text-anchor="getSizeAnchor(sectorInfo.storage.angle)" dominant-baseline="middle" :transform="`rotate(${getSizeRotation(sectorInfo.storage.angle)} ${storageInnerPos.x} ${storageInnerPos.y})`">{{ fmtSize(store.space.storage, sectorInfo.storage.angle) }}</text>
+        <text :x="storageInnerPos.x" :y="storageInnerPos.y" class="pie-label-inner" :text-anchor="getSizeAnchor(sectorInfo.storage.angle)" dominant-baseline="middle" :transform="`rotate(${getSizeRotation(sectorInfo.storage.angle)} ${storageInnerPos.x} ${storageInnerPos.y})`">{{ fmtSize(store.space.allocated, sectorInfo.storage.angle) }}</text>
         <text :x="freeInnerPos.x" :y="freeInnerPos.y" class="pie-label-inner" :text-anchor="getSizeAnchor(sectorInfo.free.angle)" dominant-baseline="middle" :transform="`rotate(${getSizeRotation(sectorInfo.free.angle)} ${freeInnerPos.x} ${freeInnerPos.y})`">{{ fmtSize(store.space.free, sectorInfo.free.angle) }}</text>
-        <text :x="otherInnerPos.x" :y="otherInnerPos.y" class="pie-label-inner" :text-anchor="getSizeAnchor(sectorInfo.other.angle)" dominant-baseline="middle" :transform="`rotate(${getSizeRotation(sectorInfo.other.angle)} ${otherInnerPos.x} ${otherInnerPos.y})`">{{ fmtSize(store.space.usage - store.space.storage, sectorInfo.other.angle) }}</text>
+        <text :x="otherInnerPos.x" :y="otherInnerPos.y" class="pie-label-inner" :text-anchor="getSizeAnchor(sectorInfo.other.angle)" dominant-baseline="middle" :transform="`rotate(${getSizeRotation(sectorInfo.other.angle)} ${otherInnerPos.x} ${otherInnerPos.y})`">{{ fmtSize(store.space.used - store.space.allocated, sectorInfo.other.angle) }}</text>
 
         <defs>
           <path :id="storageLabelPath.id" :d="storageLabelPath.d" fill="none" />
@@ -113,7 +113,7 @@ const CIRC = TAU * midRadius
 const pieStorageDash = computed(() => {
   const s = store.space
   if (!s.disk) return `0 ${CIRC}`
-  return `${(s.storage / s.disk) * CIRC} ${CIRC}`
+  return `${(s.allocated / s.disk) * CIRC} ${CIRC}`
 })
 
 const pieFreeDash = computed(() => {
@@ -125,7 +125,7 @@ const pieFreeDash = computed(() => {
 const pieFreeOffsetVal = computed(() => {
   const s = store.space
   if (!s.disk) return 0
-  return -(s.storage / s.disk) * CIRC
+  return -(s.allocated / s.disk) * CIRC
 })
 
 const freeColor = computed(() => {
@@ -153,9 +153,9 @@ const sectorInfo = computed(() => {
     other: { angle: 270, pct: 0.25 }
   }
 
-  const storagePct = s.storage / s.disk
+  const storagePct = s.allocated / s.disk
   const freePct = s.free / s.disk
-  const otherPct = (s.usage - s.storage) / s.disk
+  const otherPct = (s.used - s.allocated) / s.disk
 
   const storageAngle = storagePct * 180  // midpoint of storage sector
   const freeStart = storagePct * 360
diff --git a/frontend/src/components/FileExplorer.vue b/frontend/src/components/FileExplorer.vue
index ea1b5e0..b7691a9 100644
--- a/frontend/src/components/FileExplorer.vue
+++ b/frontend/src/components/FileExplorer.vue
@@ -124,6 +124,7 @@ defineExpose({
       dir: true,
       mtime: now,
       size: 0,
+      allocated: 0,
     })
     store.cursor = editing.value.key
   },
diff --git a/frontend/src/components/FileSize.vue b/frontend/src/components/FileSize.vue
index 432d342..5375f7f 100644
--- a/frontend/src/components/FileSize.vue
+++ b/frontend/src/components/FileSize.vue
@@ -1,22 +1,44 @@
 <template>
-  <td class="size right" :class=sizeClass>{{ doc.sizedisp }}</td>
+  <td
+    class="size right"
+    :class="sizeClass"
+    @mouseenter="doc.sparseIndicator && tooltip?.startHover($event)"
+    @mousemove="doc.sparseIndicator && tooltip?.updatePosition($event)"
+    @mouseleave="doc.sparseIndicator && tooltip?.endHover()"
+  >
+    <SparseIndicator :doc="doc" class="before-size" />{{ doc.sizedisp }}
+    <CursorTooltip v-if="doc.sparseIndicator" ref="tooltip" :text="tooltipText">{{ tooltipText }}</CursorTooltip>
+  </td>
 </template>
 
 <script setup lang="ts">
 import { Doc } from '@/repositories/Document'
-import { computed } from 'vue'
+import { computed, ref } from 'vue'
+import { formatSize } from '@/utils'
+import SparseIndicator from './SparseIndicator.vue'
+import CursorTooltip from './CursorTooltip.vue'
+
+const props = defineProps<{
+    doc: Doc
+}>()
+
+const tooltip = ref<InstanceType<typeof CursorTooltip> | null>(null)
 
 const sizeClass = computed(() => {
   const unit = props.doc.sizedisp.split('\u202F').slice(-1)[0]!
   return +unit ? "bytes" : unit
 })
 
-const props = defineProps<{
-    doc: Doc
-}>()
+const tooltipText = computed(() => {
+  const { size, allocated } = props.doc
+  return `${formatSize(allocated)} allocated of ${formatSize(size)}`
+})
 </script>
 
 <style scoped>
+.before-size {
+  margin-right: 0.2em;
+}
 .size.empty { color: #555 }
 .size.bytes { color: #77a }
 .size.kB { color: #474 }
diff --git a/frontend/src/components/Gallery.vue b/frontend/src/components/Gallery.vue
index 3caf27b..05faba2 100644
--- a/frontend/src/components/Gallery.vue
+++ b/frontend/src/components/Gallery.vue
@@ -67,6 +67,7 @@ defineExpose({
       dir: true,
       mtime: now,
       size: 0,
+      allocated: 0,
     })
     store.cursor = editing.value.key
   },
diff --git a/frontend/src/components/GalleryFigure.vue b/frontend/src/components/GalleryFigure.vue
index 01c33a2..841b71a 100644
--- a/frontend/src/components/GalleryFigure.vue
+++ b/frontend/src/components/GalleryFigure.vue
@@ -18,7 +18,7 @@
         </template>
         <template v-else>
           <SelectBox :doc=doc @click="store.cursor = doc.key"/>
-          <span>{{ doc.name }}</span>
+          <span>{{ doc.name }}<SparseIndicator :doc="doc" class="after-name" /></span>
           <div class=namespacer></div>
         </template>
       </figcaption>
@@ -26,6 +26,7 @@
     <CursorTooltip ref="tooltip" :text="tooltipText">
       <div class="tooltip-name">{{ doc.name }}</div>
       <div class="tooltip-details">{{ doc.modified }} — {{ doc.sizedisp }}</div>
+      <div v-if="doc.sparseIndicator" class="tooltip-sparse">{{ sparseText }}</div>
     </CursorTooltip>
   </a>
 </template>
@@ -34,8 +35,10 @@
 import { ref, computed } from 'vue'
 import { useMainStore } from '@/stores/main'
 import { Doc } from '@/repositories/Document'
+import { formatSize } from '@/utils'
 import MediaPreview from '@/components/MediaPreview.vue'
 import CursorTooltip from './CursorTooltip.vue'
+import SparseIndicator from './SparseIndicator.vue'
 
 const store = useMainStore()
 type EditingProp = {
@@ -52,6 +55,11 @@ const tooltip = ref<InstanceType<typeof CursorTooltip> | null>(null)
 
 const tooltipText = computed(() => props.doc.key)
 
+const sparseText = computed(() => {
+  const { size, allocated } = props.doc
+  return `${formatSize(allocated)} allocated of ${formatSize(size)}`
+})
+
 const onclick = (ev: Event) => {
   if (m.value!.play()) ev.preventDefault()
   store.cursor = props.doc.key
@@ -66,6 +74,13 @@ const onclick = (ev: Event) => {
 .tooltip-details {
   text-align: center;
 }
+.tooltip-sparse {
+  text-align: center;
+  opacity: 0.8;
+}
+.after-name {
+  margin-left: 0.3em;
+}
 figure {
   max-height: 15em;
   position: relative;
diff --git a/frontend/src/components/SparseIndicator.vue b/frontend/src/components/SparseIndicator.vue
new file mode 100644
index 0000000..4194398
--- /dev/null
+++ b/frontend/src/components/SparseIndicator.vue
@@ -0,0 +1,17 @@
+<template>
+  <span v-if="doc.sparseIndicator" class="sparse-indicator">{{ doc.sparseIndicator }}</span>
+</template>
+
+<script setup lang="ts">
+import { Doc } from '@/repositories/Document'
+
+defineProps<{
+  doc: Doc
+}>()
+</script>
+
+<style scoped>
+.sparse-indicator {
+  opacity: 0.7;
+}
+</style>
diff --git a/frontend/src/components/UploadButton.vue b/frontend/src/components/UploadButton.vue
index 6deb4ab..68c90af 100644
--- a/frontend/src/components/UploadButton.vue
+++ b/frontend/src/components/UploadButton.vue
@@ -115,13 +115,13 @@ const uploadCloudFiles = (files: CloudFile[]) => {
     for (let i = 0; i < parts.length; i++) {
       const folderPath = parts.slice(0, i + 1).join('/')
       if (folderPath && !byPath.has(folderPath) && !added.has(folderPath)) {
-        store.addGhost(new Doc({ loc: parts.slice(0, i).join('/'), name: parts[i], key: crypto.randomUUID(), size: 0, mtime: now, dir: true }))
+        store.addGhost(new Doc({ loc: parts.slice(0, i).join('/'), name: parts[i], key: crypto.randomUUID(), size: 0, allocated: 0, mtime: now, dir: true }))
         added.add(folderPath)
       }
     }
     // Ghost file or update existing (overwrite case doesn't need ghost, file already visible)
     const existing = byPath.get(f.cloudName)
-    if (!existing) store.addGhost(new Doc({ loc, name, key: crypto.randomUUID(), size: f.file.size, mtime: now, dir: false }))
+    if (!existing) store.addGhost(new Doc({ loc, name, key: crypto.randomUUID(), size: f.file.size, allocated: 0, mtime: now, dir: false }))
   }
   // @ts-ignore
   upqueue = [...upqueue, ...files]
diff --git a/frontend/src/repositories/Document.ts b/frontend/src/repositories/Document.ts
index da29d63..be5e704 100644
--- a/frontend/src/repositories/Document.ts
+++ b/frontend/src/repositories/Document.ts
@@ -7,6 +7,7 @@ export type DocProps = {
   name: string
   key: FUID
   size: number
+  allocated: number
   mtime: number
   dir: boolean
   ghost?: boolean
@@ -17,6 +18,7 @@ export class Doc {
   public loc: string = ""
   public key: FUID = ""
   public size: number = 0
+  public allocated: number = 0
   public mtime: number = 0
   public dir: boolean = false
   public ghost: boolean = false
@@ -35,6 +37,15 @@ export class Doc {
     this._name = name
   }
   get sizedisp(): string { return formatSize(this.size) }
+  /** Returns a sparse allocation indicator symbol, or empty string if fully allocated */
+  get sparseIndicator(): string {
+    if (this.dir || this.size <= this.allocated) return ''
+    if (this.allocated === 0) return '⭕'  // exactly zero
+    const ratio = this.allocated / this.size
+    // Round to nearest 25%: ◔◑◕⬤
+    const rounded = Math.round(ratio * 4)  // 0,1,2,3,4
+    return ['◔', '◔', '◑', '◕', '⬤'][rounded]!  // 0 maps to ◔ since we handled exact 0 above
+  }
   get modified(): string { return formatUnixDate(this.mtime) }
   get url(): string {
     const p = this.loc ? `${this.loc}/${this.name}` : this.name
@@ -78,9 +89,10 @@ export type FileEntry = [
   number,  // level
   string,  // name
   FUID,
-  number, //mtime
-  number, // size
-  number, // isfile
+  number,  // mtime
+  number,  // size
+  number,  // allocated (actual disk usage)
+  number,  // isfile
 ]
 
 export type UpdateEntry = ['k', number] | ['d', number] | ['i', Array<FileEntry>]
diff --git a/frontend/src/stores/main.ts b/frontend/src/stores/main.ts
index 4aa8bcd..5d740e9 100644
--- a/frontend/src/stores/main.ts
+++ b/frontend/src/stores/main.ts
@@ -96,8 +96,9 @@ export const useMainStore = defineStore('main', {
     space: {
       disk: 0,
       free: 0,
-      usage: 0,
+      used: 0,
       storage: 0,
+      allocated: 0,
     }
   }),
   persist: {
@@ -118,13 +119,14 @@ export const useMainStore = defineStore('main', {
     updateRoot(root: FileEntry[]) {
       const docs = []
       let loc = [] as string[]
-      for (const [level, name, key, mtime, size, isfile] of root) {
+      for (const [level, name, key, mtime, size, allocated, isfile] of root) {
         loc = loc.slice(0, level - 1)
         docs.push(new Doc({
           name,
           loc: level ? loc.join('/') : '/',
           key,
           size,
+          allocated,
           mtime,
           dir: !isfile,
         }))
diff --git a/tests/test_watching.py b/tests/test_watching.py
index c358469..8034839 100644
--- a/tests/test_watching.py
+++ b/tests/test_watching.py
@@ -10,7 +10,9 @@ def decode(data: str):
 
 # Helper function to create a list of FileEntry objects
 def f(count, start=0):
-    return [FileEntry(i, str(i), str(i), 0, 0, 0) for i in range(start, start + count)]
+    return [
+        FileEntry(i, str(i), str(i), 0, 0, 0, 0) for i in range(start, start + count)
+    ]
 
 
 def test_identical_lists():
@@ -35,8 +37,8 @@ def test_insertions():
 
 
 def test_insertion_at_end():
-    old_list = [*f(3), FileEntry(1, "xxx", "xxx", 0, 0, 1)]
-    newfile = FileEntry(1, "yyy", "yyy", 0, 0, 1)
+    old_list = [*f(3), FileEntry(1, "xxx", "xxx", 0, 0, 0, 1)]
+    newfile = FileEntry(1, "yyy", "yyy", 0, 0, 0, 1)
     new_list = [*old_list, newfile]
     expected = [UpdKeep(4), UpdIns([newfile])]
     assert decode(format_update(old_list, new_list)) == expected