diff --git a/lib/airdrop/sql.test.ts b/lib/airdrop/sql.test.ts
index 4a61e5a..ff01fe5 100644
--- a/lib/airdrop/sql.test.ts
+++ b/lib/airdrop/sql.test.ts
@@ -58,6 +58,10 @@ beforeAll(async () => {
       referred_address TEXT NOT NULL
     );
   `);
+  const migrationSql = await import("fs").then(fs =>
+    fs.readFileSync(new URL("../../supabase/migrations/00040_weighted_spend_function.sql", import.meta.url), "utf-8")
+  );
+  await db.exec(migrationSql.replace(/GRANT[^;]*;/, ""));
 });
 
 afterAll(async () => {
diff --git a/lib/airdrop/sql.ts b/lib/airdrop/sql.ts
index a7eccb6..963e383 100644
--- a/lib/airdrop/sql.ts
+++ b/lib/airdrop/sql.ts
@@ -24,62 +24,7 @@ export function weightedSpendQuery(config: AirdropConfig): WeightedSpendQuery {
     config.REFERRAL_MULTIPLIER_CAP,
   ];
 
-  const sql = `
-WITH eligible AS (
-  SELECT
-    a.address,
-    CASE WHEN a.fid IS NOT NULL THEN 1 ELSE 0 END AS has_fc_bonus
-  FROM pl_activations a
-  WHERE a.activated_at IS NOT NULL
-    AND a.is_blacklisted = FALSE
-),
-buys AS (
-  SELECT p.address, COALESCE(SUM(p.points), 0) AS buy_volume
-  FROM pl_points p
-  WHERE p.action = 'buy'
-    AND p.created_at >= $1
-    AND p.created_at <= $2
-  GROUP BY p.address
-),
-eligible_buys AS (
-  SELECT e.address, e.has_fc_bonus, COALESCE(b.buy_volume, 0) AS buy_volume
-  FROM eligible e
-  JOIN buys b ON e.address = b.address
-),
-qualified_refs AS (
-  SELECT r.referrer_address AS address, COUNT(*) AS ref_count
-  FROM pl_referrals r
-  JOIN eligible_buys eb ON r.referred_address = eb.address
-  WHERE eb.buy_volume >= $3
-  GROUP BY r.referrer_address
-),
-weighted AS (
-  SELECT
-    eb.address,
-    eb.buy_volume,
-    COALESCE(qr.ref_count, 0) AS qualified_refs,
-    eb.has_fc_bonus,
-    LEAST(
-      1 + (COALESCE(qr.ref_count, 0) + eb.has_fc_bonus) * $4::NUMERIC,
-      $5::NUMERIC
-    ) AS multiplier,
-    eb.buy_volume * LEAST(
-      1 + (COALESCE(qr.ref_count, 0) + eb.has_fc_bonus) * $4::NUMERIC,
-      $5::NUMERIC
-    ) AS weighted_spend
-  FROM eligible_buys eb
-  LEFT JOIN qualified_refs qr ON eb.address = qr.address
-)
-SELECT
-  w.address,
-  w.buy_volume,
-  w.qualified_refs,
-  w.has_fc_bonus,
-  w.multiplier,
-  w.weighted_spend,
-  SUM(w.weighted_spend) OVER () AS community_total
-FROM weighted w
-`.trim();
+  const sql = `SELECT * FROM weighted_spend($1::TIMESTAMPTZ, $2::TIMESTAMPTZ, $3::NUMERIC, $4::NUMERIC, $5::NUMERIC)`;
 
   return { sql, params };
 }
diff --git a/lib/supabase.ts b/lib/supabase.ts
index 066eeab..5b43ec2 100644
--- a/lib/supabase.ts
+++ b/lib/supabase.ts
@@ -797,6 +797,24 @@ export interface Database {
         Args: { p_key: string; p_max_requests: number; p_window_ms: number };
         Returns: boolean;
       };
+      weighted_spend: {
+        Args: {
+          p_campaign_start: string;
+          p_campaign_end: string;
+          p_min_referral_threshold: number;
+          p_multiplier_per_ref: number;
+          p_multiplier_cap: number;
+        };
+        Returns: Array<{
+          address: string;
+          buy_volume: number;
+          qualified_refs: number;
+          has_fc_bonus: number;
+          multiplier: number;
+          weighted_spend: number;
+          community_total: number;
+        }>;
+      };
     };
     Enums: {
       [_ in never]: never;
diff --git a/package-lock.json b/package-lock.json
index 97ad5f8..e8350fb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "plotlink",
-  "version": "1.32.2",
+  "version": "1.33.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "plotlink",
-      "version": "1.32.2",
+      "version": "1.33.0",
       "workspaces": [
         "packages/*"
       ],
diff --git a/package.json b/package.json
index 211044a..96d16ff 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "plotlink",
-  "version": "1.32.2",
+  "version": "1.33.0",
   "private": true,
   "workspaces": [
     "packages/*"
diff --git a/src/app/api/airdrop/projection/route.test.ts b/src/app/api/airdrop/projection/route.test.ts
new file mode 100644
index 0000000..f631a92
--- /dev/null
+++ b/src/app/api/airdrop/projection/route.test.ts
@@ -0,0 +1,125 @@
+// @vitest-environment node
+import { describe, expect, it, vi } from "vitest";
+
+const mockRpc = vi.fn();
+const mockActivationSingle = vi.fn();
+
+vi.mock("../../../../../lib/supabase", () => ({
+  createServerClient: () => ({
+    rpc: mockRpc,
+    from: (table: string) => {
+      if (table === "pl_activations") {
+        return { select: () => ({ eq: () => ({ single: mockActivationSingle }) }) };
+      }
+      return {};
+    },
+  }),
+}));
+vi.mock("../../../../../lib/airdrop/config", () => ({
+  getAirdropConfig: () => ({
+    CAMPAIGN_START: new Date("2026-07-01"),
+    CAMPAIGN_END: new Date("2026-10-01"),
+    POOL_AMOUNT: 200_000,
+    MILESTONES: {
+      BRONZE: { mcap: 100_000, pct: 10 },
+      SILVER: { mcap: 1_000_000, pct: 30 },
+      GOLD: { mcap: 5_000_000, pct: 50 },
+      DIAMOND: { mcap: 10_000_000, pct: 100 },
+    },
+    MIN_REFERRAL_THRESHOLD: 50,
+    REFERRAL_MULTIPLIER_PER_REF: 0.2,
+    REFERRAL_MULTIPLIER_CAP: 3.0,
+  }),
+}));
+
+import { GET } from "./route";
+
+function makeReq(address?: string) {
+  const url = address
+    ? `http://localhost/api/airdrop/projection?address=${address}`
+    : "http://localhost/api/airdrop/projection";
+  return new Request(url);
+}
+
+describe("GET /api/airdrop/projection", () => {
+  it("§4 worked example: 100 PLOT + 2 refs + FC → 1.6x, weighted 160", async () => {
+    const ref1Ws = 60;
+    const ref2Ws = 80;
+    const aliceWs = 160;
+    const total = aliceWs + ref1Ws + ref2Ws;
+
+    mockRpc.mockResolvedValue({
+      data: [
+        { address: "alice", buy_volume: 100, qualified_refs: 2, has_fc_bonus: 1, multiplier: 1.6, weighted_spend: 160, community_total: total },
+        { address: "ref1", buy_volume: 60, qualified_refs: 0, has_fc_bonus: 0, multiplier: 1, weighted_spend: 60, community_total: total },
+        { address: "ref2", buy_volume: 80, qualified_refs: 0, has_fc_bonus: 0, multiplier: 1, weighted_spend: 80, community_total: total },
+      ],
+      error: null,
+    });
+
+    const res = await GET(makeReq("alice"));
+    expect(res.status).toBe(200);
+    const data = await res.json();
+
+    expect(data.buy_volume).toBe(100);
+    expect(data.qualified_refs).toBe(2);
+    expect(data.has_fc_bonus).toBe(true);
+    expect(data.multiplier).toBeCloseTo(1.6);
+    expect(data.weighted_spend).toBeCloseTo(160);
+    expect(data.community_total).toBeCloseTo(total);
+
+    const share = 160 / total;
+    expect(data.projected_share.bronze).toBeCloseTo(200_000 * 0.10 * share);
+    expect(data.projected_share.silver).toBeCloseTo(200_000 * 0.30 * share);
+    expect(data.projected_share.gold).toBeCloseTo(200_000 * 0.50 * share);
+    expect(data.projected_share.diamond).toBeCloseTo(200_000 * 1.00 * share);
+  });
+
+  it("returns zeros for activated wallet with no buys", async () => {
+    mockRpc.mockResolvedValue({ data: [], error: null });
+    mockActivationSingle.mockResolvedValue({ data: { activated_at: "2026-07-01", is_blacklisted: false } });
+
+    const res = await GET(makeReq("alice"));
+    expect(res.status).toBe(200);
+    const data = await res.json();
+    expect(data.buy_volume).toBe(0);
+    expect(data.weighted_spend).toBe(0);
+    expect(data.projected_share.diamond).toBe(0);
+  });
+
+  it("returns 404 for non-activated wallet", async () => {
+    mockRpc.mockResolvedValue({ data: [], error: null });
+    mockActivationSingle.mockResolvedValue({ data: null });
+
+    const res = await GET(makeReq("0xnone"));
+    expect(res.status).toBe(404);
+  });
+
+  it("returns 404 for blacklisted wallet", async () => {
+    mockRpc.mockResolvedValue({ data: [], error: null });
+    mockActivationSingle.mockResolvedValue({ data: { activated_at: "2026-07-01", is_blacklisted: true } });
+
+    const res = await GET(makeReq("bad"));
+    expect(res.status).toBe(404);
+  });
+
+  it("includes Cache-Control: public, max-age=30", async () => {
+    mockRpc.mockResolvedValue({ data: [], error: null });
+    mockActivationSingle.mockResolvedValue({ data: { activated_at: "2026-07-01", is_blacklisted: false } });
+
+    const res = await GET(makeReq("alice"));
+    expect(res.headers.get("Cache-Control")).toBe("public, max-age=30");
+  });
+
+  it("returns 400 when address is missing", async () => {
+    const res = await GET(makeReq());
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 500 when RPC fails", async () => {
+    mockRpc.mockResolvedValue({ data: null, error: { message: "function not found" } });
+
+    const res = await GET(makeReq("alice"));
+    expect(res.status).toBe(500);
+  });
+});
diff --git a/src/app/api/airdrop/projection/route.ts b/src/app/api/airdrop/projection/route.ts
new file mode 100644
index 0000000..1ea12f0
--- /dev/null
+++ b/src/app/api/airdrop/projection/route.ts
@@ -0,0 +1,93 @@
+import { NextResponse } from "next/server";
+import { createServerClient } from "../../../../../lib/supabase";
+import { getAirdropConfig } from "../../../../../lib/airdrop/config";
+import type { WeightedSpendRow } from "../../../../../lib/airdrop/sql";
+
+export async function GET(req: Request) {
+  const { searchParams } = new URL(req.url);
+  const address = searchParams.get("address")?.toLowerCase();
+
+  if (!address) {
+    return NextResponse.json({ error: "address parameter required" }, { status: 400 });
+  }
+
+  const supabase = createServerClient();
+  if (!supabase) {
+    return NextResponse.json({ error: "Supabase not configured" }, { status: 500 });
+  }
+
+  const config = getAirdropConfig();
+
+  const { data: rows, error } = await supabase.rpc("weighted_spend", {
+    p_campaign_start: config.CAMPAIGN_START.toISOString(),
+    p_campaign_end: config.CAMPAIGN_END.toISOString(),
+    p_min_referral_threshold: config.MIN_REFERRAL_THRESHOLD,
+    p_multiplier_per_ref: config.REFERRAL_MULTIPLIER_PER_REF,
+    p_multiplier_cap: config.REFERRAL_MULTIPLIER_CAP,
+  });
+
+  if (error) {
+    console.error("[projection] weighted_spend RPC failed:", error.message);
+    return NextResponse.json({ error: "Failed to compute projection" }, { status: 500 });
+  }
+
+  const allRows = (rows ?? []) as WeightedSpendRow[];
+  const me = allRows.find(r => r.address === address);
+
+  if (!me) {
+    const { data: activation } = await supabase
+      .from("pl_activations")
+      .select("activated_at, is_blacklisted")
+      .eq("address", address)
+      .single();
+
+    if (!activation || !activation.activated_at || activation.is_blacklisted) {
+      return NextResponse.json(
+        { error: "Wallet not activated or not eligible" },
+        { status: 404, headers: { "Cache-Control": "public, max-age=30" } },
+      );
+    }
+
+    return NextResponse.json(
+      {
+        address,
+        buy_volume: 0,
+        qualified_refs: 0,
+        has_fc_bonus: false,
+        multiplier: 1,
+        weighted_spend: 0,
+        community_total: Number(allRows[0]?.community_total ?? 0),
+        projected_share: { bronze: 0, silver: 0, gold: 0, diamond: 0 },
+      },
+      { headers: { "Cache-Control": "public, max-age=30" } },
+    );
+  }
+
+  const buyVolume = Number(me.buy_volume);
+  const qualifiedRefs = Number(me.qualified_refs);
+  const hasFcBonus = Number(me.has_fc_bonus) === 1;
+  const multiplier = Number(me.multiplier);
+  const weightedSpend = Number(me.weighted_spend);
+  const communityTotal = Number(me.community_total);
+  const share = communityTotal > 0 ? weightedSpend / communityTotal : 0;
+  const pool = config.POOL_AMOUNT;
+
+  return NextResponse.json(
+    {
+      address,
+      buy_volume: buyVolume,
+      qualified_refs: qualifiedRefs,
+      has_fc_bonus: hasFcBonus,
+      multiplier,
+      weighted_spend: weightedSpend,
+      community_total: communityTotal,
+      projected_share: {
+        bronze: pool * (config.MILESTONES.BRONZE.pct / 100) * share,
+        silver: pool * (config.MILESTONES.SILVER.pct / 100) * share,
+        gold: pool * (config.MILESTONES.GOLD.pct / 100) * share,
+        diamond: pool * (config.MILESTONES.DIAMOND.pct / 100) * share,
+      },
+    },
+    { headers: { "Cache-Control": "public, max-age=30" } },
+  );
+}
diff --git a/supabase/migrations/00040_weighted_spend_function.sql b/supabase/migrations/00040_weighted_spend_function.sql
new file mode 100644
index 0000000..e7290e3
--- /dev/null
+++ b/supabase/migrations/00040_weighted_spend_function.sql
@@ -0,0 +1,75 @@
+CREATE OR REPLACE FUNCTION weighted_spend(
+  p_campaign_start TIMESTAMPTZ,
+  p_campaign_end TIMESTAMPTZ,
+  p_min_referral_threshold NUMERIC,
+  p_multiplier_per_ref NUMERIC,
+  p_multiplier_cap NUMERIC
+)
+RETURNS TABLE (
+  address TEXT,
+  buy_volume NUMERIC,
+  qualified_refs BIGINT,
+  has_fc_bonus INTEGER,
+  multiplier NUMERIC,
+  weighted_spend NUMERIC,
+  community_total NUMERIC
+)
+LANGUAGE SQL STABLE
+AS $$
+  WITH eligible AS (
+    SELECT
+      a.address,
+      CASE WHEN a.fid IS NOT NULL THEN 1 ELSE 0 END AS has_fc_bonus
+    FROM pl_activations a
+    WHERE a.activated_at IS NOT NULL
+      AND a.is_blacklisted = FALSE
+  ),
+  buys AS (
+    SELECT p.address, COALESCE(SUM(p.points), 0) AS buy_volume
+    FROM pl_points p
+    WHERE p.action = 'buy'
+      AND p.created_at >= p_campaign_start
+      AND p.created_at <= p_campaign_end
+    GROUP BY p.address
+  ),
+  eligible_buys AS (
+    SELECT e.address, e.has_fc_bonus, COALESCE(b.buy_volume, 0) AS buy_volume
+    FROM eligible e
+    JOIN buys b ON e.address = b.address
+  ),
+  qualified_refs AS (
+    SELECT r.referrer_address AS address, COUNT(*) AS ref_count
+    FROM pl_referrals r
+    JOIN eligible_buys eb ON r.referred_address = eb.address
+    WHERE eb.buy_volume >= p_min_referral_threshold
+    GROUP BY r.referrer_address
+  ),
+  weighted AS (
+    SELECT
+      eb.address,
+      eb.buy_volume,
+      COALESCE(qr.ref_count, 0) AS qualified_refs,
+      eb.has_fc_bonus,
+      LEAST(
+        1 + (COALESCE(qr.ref_count, 0) + eb.has_fc_bonus) * p_multiplier_per_ref,
+        p_multiplier_cap
+      ) AS multiplier,
+      eb.buy_volume * LEAST(
+        1 + (COALESCE(qr.ref_count, 0) + eb.has_fc_bonus) * p_multiplier_per_ref,
+        p_multiplier_cap
+      ) AS weighted_spend
+    FROM eligible_buys eb
+    LEFT JOIN qualified_refs qr ON eb.address = qr.address
+  )
+  SELECT
+    w.address,
+    w.buy_volume,
+    w.qualified_refs,
+    w.has_fc_bonus,
+    w.multiplier,
+    w.weighted_spend,
+    SUM(w.weighted_spend) OVER () AS community_total
+  FROM weighted w;
+$$;
+
+GRANT EXECUTE ON FUNCTION weighted_spend TO service_role;