diff --git a/web/components/bet-panel.tsx b/web/components/bet-panel.tsx
index afb5bfd2..bcb18b47 100644
--- a/web/components/bet-panel.tsx
+++ b/web/components/bet-panel.tsx
@@ -64,7 +64,7 @@ export function BetPanel(props: { contract: Contract; className?: string }) {
   return (
     <Col
       className={clsx(
-        'bg-gray-200 shadow-xl px-8 py-6 rounded w-full md:w-auto',
+        'bg-gray-200 shadow-xl px-8 py-6 rounded-md w-full md:w-auto',
         className
       )}
     >
diff --git a/web/components/contract-overview.tsx b/web/components/contract-overview.tsx
index 41fea05b..659e62f9 100644
--- a/web/components/contract-overview.tsx
+++ b/web/components/contract-overview.tsx
@@ -1,51 +1,22 @@
 import React from 'react'
-import { Line } from 'react-chartjs-2'
-import {
-  CategoryScale,
-  Chart,
-  LinearScale,
-  PointElement,
-  LineElement,
-  Title,
-  Tooltip,
-  Legend,
-} from 'chart.js'
 import { Contract } from '../lib/firebase/contracts'
 import { Col } from './layout/col'
 import { Row } from './layout/row'
 import { Spacer } from './layout/spacer'
 import { formatWithCommas } from '../lib/util/format'
+import { ContractProbGraph } from './contract-prob-graph'
 
-// Auto import doesn't work for some reason...
-// So we manually register ChartJS components instead:
-Chart.register(
-  CategoryScale,
-  LinearScale,
-  PointElement,
-  LineElement,
-  Title,
-  Tooltip,
-  Legend
-)
-const chartData = {
-  labels: Array.from({ length: 0 }, (_, i) => i + 1),
-  datasets: [
-    {
-      label: 'Implied probability',
-      data: [],
-      borderColor: 'rgb(75, 192, 192)',
-    },
-  ],
-}
-
-export const ContractOverview = (props: { contract: Contract }) => {
-  const { contract } = props
+export const ContractOverview = (props: {
+  contract: Contract
+  className?: string
+}) => {
+  const { contract, className } = props
   const { pot, seedAmounts } = contract
 
   const volume = pot.YES + pot.NO - seedAmounts.YES - seedAmounts.NO
 
   return (
-    <Col className="max-w-3xl w-full">
+    <Col className={className}>
       <div className="text-3xl font-medium p-2">{contract.question}</div>
 
       <Row className="flex-wrap text-sm text-gray-600">
@@ -53,12 +24,14 @@ export const ContractOverview = (props: { contract: Contract }) => {
         <div className="py-2">•</div>
         <div className="p-2 whitespace-nowrap">Dec 9</div>
         <div className="py-2">•</div>
-        <div className="p-2 whitespace-nowrap">{formatWithCommas(volume)} volume</div>
+        <div className="p-2 whitespace-nowrap">
+          {formatWithCommas(volume)} volume
+        </div>
       </Row>
 
       <Spacer h={4} />
 
-      <Line data={chartData} height={150} />
+      <ContractProbGraph contract={contract} />
 
       <Spacer h={12} />
 
diff --git a/web/components/contract-prob-graph.tsx b/web/components/contract-prob-graph.tsx
new file mode 100644
index 00000000..ad05ec6d
--- /dev/null
+++ b/web/components/contract-prob-graph.tsx
@@ -0,0 +1,52 @@
+import { Line } from 'react-chartjs-2'
+import {
+  CategoryScale,
+  Chart,
+  LinearScale,
+  PointElement,
+  LineElement,
+  Title,
+  Tooltip,
+  Legend,
+} from 'chart.js'
+
+import { useBets } from '../hooks/use-bets'
+import { Contract } from '../lib/firebase/contracts'
+
+// Auto import doesn't work for some reason...
+// So we manually register ChartJS components instead:
+Chart.register(
+  CategoryScale,
+  LinearScale,
+  PointElement,
+  LineElement,
+  Title,
+  Tooltip,
+  Legend
+)
+
+export function ContractProbGraph(props: { contract: Contract }) {
+  const { contract } = props
+  const { id, seedAmounts } = contract
+
+  let bets = useBets(id)
+  if (bets === 'loading') bets = []
+
+  const seedProb =
+    seedAmounts.YES ** 2 / (seedAmounts.YES ** 2 + seedAmounts.NO ** 2)
+
+  const probs = [seedProb, ...bets.map((bet) => bet.probAfter)]
+
+  const chartData = {
+    labels: Array.from({ length: probs.length }, (_, i) => i + 1),
+    datasets: [
+      {
+        label: 'Implied probability',
+        data: probs,
+        borderColor: 'rgb(75, 192, 192)',
+      },
+    ],
+  }
+
+  return <Line data={chartData} height={150} />
+}
diff --git a/web/hooks/use-bets.ts b/web/hooks/use-bets.ts
new file mode 100644
index 00000000..0a35ba53
--- /dev/null
+++ b/web/hooks/use-bets.ts
@@ -0,0 +1,12 @@
+import { useEffect, useState } from 'react'
+import { Bet, listenForBets } from '../lib/firebase/bets'
+
+export const useBets = (contractId: string) => {
+  const [bets, setBets] = useState<Bet[] | 'loading'>('loading')
+
+  useEffect(() => {
+    if (contractId) return listenForBets(contractId, setBets)
+  }, [contractId])
+
+  return bets
+}
diff --git a/web/lib/firebase/bets.ts b/web/lib/firebase/bets.ts
index dbfd6f2b..79036c44 100644
--- a/web/lib/firebase/bets.ts
+++ b/web/lib/firebase/bets.ts
@@ -1,22 +1,32 @@
-import { doc, setDoc } from 'firebase/firestore'
+import { collection, onSnapshot } from 'firebase/firestore'
 import { db } from './init'
 
 export type Bet = {
   id: string
   userId: string
   contractId: string
-
-  amount: number // Amount of USD bid
+  amount: number // Amount of bet
   outcome: 'YES' | 'NO' // Chosen outcome
-
-  // Calculate and replace these on server?
-  createdTime: number
   dpmWeight: number // Dynamic Parimutuel weight
+  probBefore: number
+  probAverage: number
+  probAfter: number
+  createdTime: number
 }
 
-// Push bet to Firestore
-// TODO: Should bets be subcollections under its contract?
-export async function saveBet(bet: Bet) {
-  const docRef = doc(db, 'contracts', bet.contractId, 'bets', bet.id)
-  await setDoc(docRef, bet)
+function getBetsCollection(contractId: string) {
+  return collection(db, 'contracts', contractId, 'bets')
+}
+
+export function listenForBets(
+  contractId: string,
+  setBets: (bets: Bet[]) => void
+) {
+  return onSnapshot(getBetsCollection(contractId), (snap) => {
+    const bets = snap.docs.map((doc) => doc.data() as Bet)
+
+    bets.sort((bet1, bet2) => bet1.createdTime - bet2.createdTime)
+
+    setBets(bets)
+  })
 }
diff --git a/web/pages/contract/[contractId].tsx b/web/pages/contract/[contractId].tsx
index bcde85fa..365a5a77 100644
--- a/web/pages/contract/[contractId].tsx
+++ b/web/pages/contract/[contractId].tsx
@@ -24,15 +24,13 @@ export default function ContractPage() {
     <div className="max-w-7xl mx-auto sm:px-6 lg:px-8">
       <Header />
 
-      <div className="w-full flex flex-col p-4 mt-4">
-        <Col className="md:justify-between md:flex-row">
-          <ContractOverview contract={contract} />
+      <Col className="w-full md:justify-between md:flex-row p-4 mt-4">
+        <ContractOverview contract={contract} className="max-w-4xl w-full" />
 
-          <div className="mt-12 md:mt-0" />
+        <div className="mt-12 md:mt-0" />
 
-          <BetPanel className="self-start" contract={contract} />
-        </Col>
-      </div>
+        <BetPanel className="self-start" contract={contract} />
+      </Col>
     </div>
   )
 }