diff --git a/scripts/README.md b/scripts/README.md
index 40c2a27..8755fee 100644
--- a/scripts/README.md
+++ b/scripts/README.md
@@ -49,3 +49,26 @@ If something goes wrong mid-run, the backup JSON contains the pre-migration stat
 - Identify which members had `helcimSubscriptionId` before it was unset.
 
 Backup files are gitignored (`.migration-backup-*.json`).
+
+---
+
+## migrate-contribution-amount.cjs
+
+One-time migration: converts `Member.contributionTier` (String enum) to
+`Member.contributionAmount` (Number). Idempotent — only touches documents that
+still have the legacy field.
+
+### Usage
+
+```bash
+node scripts/migrate-contribution-amount.cjs           # dry-run
+node scripts/migrate-contribution-amount.cjs --apply   # write
+```
+
+### What it does
+
+Iterates members with `contributionTier` still set, parses each value as an integer
+(valid: `"0"`, `"5"`, `"15"`, `"30"`, `"50"`), and writes the converted value to
+`contributionAmount`. Unsets the old field. Skips any record that cannot be parsed.
+
+Safe to re-run: only matches members where `contributionTier` still exists.
diff --git a/scripts/migrate-contribution-amount.cjs b/scripts/migrate-contribution-amount.cjs
new file mode 100644
index 0000000..406cc1a
--- /dev/null
+++ b/scripts/migrate-contribution-amount.cjs
@@ -0,0 +1,67 @@
+/**
+ * One-time migration: Member.contributionTier (String: "0"|"5"|"15"|"30"|"50") →
+ * Member.contributionAmount (Number). Idempotent: only acts on docs that still
+ * have contributionTier; safe to re-run.
+ *
+ * Usage:
+ *   node scripts/migrate-contribution-amount.cjs            # dry-run (default)
+ *   node scripts/migrate-contribution-amount.cjs --apply    # writes changes
+ */
+require('dotenv').config()
+const mongoose = require('mongoose')
+
+async function run() {
+  const apply = process.argv.includes('--apply')
+  if (!process.env.MONGODB_URI) {
+    console.error('MONGODB_URI not set in environment')
+    process.exit(1)
+  }
+
+  await mongoose.connect(process.env.MONGODB_URI)
+  const db = mongoose.connection.db
+  const col = db.collection('members')
+
+  // Count docs that still have the old field
+  const legacyCount = await col.countDocuments({ contributionTier: { $exists: true } })
+  console.log(`Found ${legacyCount} members with legacy contributionTier`)
+
+  if (legacyCount === 0) {
+    console.log('Nothing to migrate.')
+    await mongoose.disconnect()
+    return
+  }
+
+  const cursor = col.find({ contributionTier: { $exists: true } })
+  let updated = 0
+  let skipped = 0
+
+  while (await cursor.hasNext()) {
+    const doc = await cursor.next()
+    const raw = doc.contributionTier
+    const amount = parseInt(raw, 10)
+    if (!Number.isInteger(amount) || amount < 0) {
+      console.warn(`  SKIP ${doc._id}: cannot parse contributionTier=${JSON.stringify(raw)}`)
+      skipped++
+      continue
+    }
+    if (apply) {
+      await col.updateOne(
+        { _id: doc._id },
+        { $set: { contributionAmount: amount }, $unset: { contributionTier: '' } },
+      )
+    }
+    updated++
+  }
+
+  console.log(`${apply ? 'Updated' : 'Would update'} ${updated} documents, skipped ${skipped}`)
+  if (!apply) console.log('Dry-run complete. Re-run with --apply to write changes.')
+  await mongoose.disconnect()
+}
+
+run().catch(async (err) => {
+  console.error(err)
+  try {
+    await mongoose.disconnect()
+  } catch {}
+  process.exit(1)
+})