diff --git a/common/antes.ts b/common/antes.ts
index 5f269083..f94c9f35 100644
--- a/common/antes.ts
+++ b/common/antes.ts
@@ -1,3 +1,8 @@
+import { Bet } from './bet'
+import { getProbability } from './calculate'
+import { Contract } from './contract'
+import { User } from './user'
+
 export const PHANTOM_ANTE = 200
 
 export const calcStartPool = (initialProbInt: number, ante = 0) => {
@@ -15,3 +20,39 @@ export const calcStartPool = (initialProbInt: number, ante = 0) => {
 
   return { sharesYes, sharesNo, poolYes, poolNo, startYes, startNo }
 }
+
+export function getAnteBets(
+  creator: User,
+  contract: Contract,
+  yesAnteId: string,
+  noAnteId: string
+) {
+  const p = getProbability(contract.totalShares)
+  const ante = contract.totalBets.YES + contract.totalBets.NO
+
+  const yesBet: Bet = {
+    id: yesAnteId,
+    userId: creator.id,
+    contractId: contract.id,
+    amount: p * ante,
+    shares: Math.sqrt(p) * ante,
+    outcome: 'YES',
+    probBefore: p,
+    probAfter: p,
+    createdTime: Date.now(),
+  }
+
+  const noBet: Bet = {
+    id: noAnteId,
+    userId: creator.id,
+    contractId: contract.id,
+    amount: (1 - p) * ante,
+    shares: Math.sqrt(1 - p) * ante,
+    outcome: 'NO',
+    probBefore: p,
+    probAfter: p,
+    createdTime: Date.now(),
+  }
+
+  return { yesBet, noBet }
+}
diff --git a/common/calculate.ts b/common/calculate.ts
index 5468588e..ef81fd72 100644
--- a/common/calculate.ts
+++ b/common/calculate.ts
@@ -36,6 +36,22 @@ export function calculateShares(
     : Math.sqrt(bet ** 2 + noShares ** 2 + c) - noShares
 }
 
+export function calculateEstimatedWinnings(
+  totalShares: { YES: number; NO: number },
+  shares: number,
+  betChoice: 'YES' | 'NO'
+) {
+  const ind = betChoice === 'YES' ? 1 : 0
+
+  const yesShares = totalShares.YES + ind * shares
+  const noShares = totalShares.NO + (1 - ind) * shares
+
+  const estPool = Math.sqrt(yesShares ** 2 + noShares ** 2)
+  const total = ind * yesShares + (1 - ind) * noShares
+
+  return (shares * estPool) / total
+}
+
 export function calculateRawShareValue(
   totalShares: { YES: number; NO: number },
   shares: number,
@@ -112,15 +128,35 @@ export function calculateStandardPayout(
   if (totalBets[outcome] >= truePool)
     return (amount / totalBets[outcome]) * truePool
 
-  const startShares = startPool.YES + startPool.NO
-  const total = totalShares[outcome] - startShares - totalBets[outcome]
+  const total = totalShares[outcome] - startPool[outcome] - totalBets[outcome]
   const winningsPool = truePool - totalBets[outcome]
 
   return (1 - FEES) * (amount + ((shares - amount) / total) * winningsPool)
 }
 
 export function calculatePayoutAfterCorrectBet(contract: Contract, bet: Bet) {
-  return calculateStandardPayout(contract, bet, bet.outcome)
+  const { totalShares, pool, totalBets } = contract
+
+  const ind = bet.outcome === 'YES' ? 1 : 0
+  const { shares, amount } = bet
+
+  const newContract = {
+    ...contract,
+    totalShares: {
+      YES: totalShares.YES + ind * shares,
+      NO: totalShares.NO + (1 - ind) * shares,
+    },
+    pool: {
+      YES: pool.YES + ind * amount,
+      NO: pool.NO + (1 - ind) * amount,
+    },
+    totalBets: {
+      YES: totalBets.YES + ind * amount,
+      NO: totalBets.NO + (1 - ind) * amount,
+    },
+  }
+
+  return calculateStandardPayout(newContract, bet, bet.outcome)
 }
 
 function calculateMktPayout(contract: Contract, bet: Bet) {
diff --git a/common/new-contract.ts b/common/new-contract.ts
index e3da778d..b2fb08b5 100644
--- a/common/new-contract.ts
+++ b/common/new-contract.ts
@@ -1,4 +1,5 @@
 import { calcStartPool } from './antes'
+
 import { Contract } from './contract'
 import { User } from './user'
 
@@ -45,5 +46,3 @@ export function getNewContract(
 
   return contract
 }
-
-function getAnteBets() {}
diff --git a/functions/src/create-contract.ts b/functions/src/create-contract.ts
index dbe3806b..779b38d4 100644
--- a/functions/src/create-contract.ts
+++ b/functions/src/create-contract.ts
@@ -6,6 +6,7 @@ import { Contract } from '../../common/contract'
 import { slugify } from '../../common/util/slugify'
 import { randomString } from '../../common/util/random-string'
 import { getNewContract } from '../../common/new-contract'
+import { getAnteBets } from '../../common/antes'
 
 export const createContract = functions
   .runWith({ minInstances: 1 })
@@ -64,6 +65,26 @@ export const createContract = functions
       if (ante) await chargeUser(creator.id, ante)
 
       await contractRef.create(contract)
+
+      if (ante) {
+        const yesBetDoc = firestore
+          .collection(`contracts/${contract.id}/bets`)
+          .doc()
+
+        const noBetDoc = firestore
+          .collection(`contracts/${contract.id}/bets`)
+          .doc()
+
+        const { yesBet, noBet } = getAnteBets(
+          creator,
+          contract,
+          yesBetDoc.id,
+          noBetDoc.id
+        )
+        await yesBetDoc.set(yesBet)
+        await noBetDoc.set(noBet)
+      }
+
       return { status: 'success', contract }
     }
   )
diff --git a/web/components/bet-panel.tsx b/web/components/bet-panel.tsx
index 53fd89f7..1309e9b2 100644
--- a/web/components/bet-panel.tsx
+++ b/web/components/bet-panel.tsx
@@ -18,6 +18,7 @@ import {
   calculateShares,
   getProbabilityAfterBet,
   calculatePayoutAfterCorrectBet,
+  calculateEstimatedWinnings,
 } from '../../common/calculate'
 import { firebaseLogin } from '../lib/firebase/users'
 import { OutcomeLabel } from './outcome-label'
@@ -84,18 +85,30 @@ export function BetPanel(props: { contract: Contract; className?: string }) {
 
   const betDisabled = isSubmitting || !betAmount || error
 
-  const initialProb = getProbability(contract.pool)
+  const initialProb = getProbability(contract.totalShares)
+
   const resultProb = getProbabilityAfterBet(
     contract.totalShares,
     betChoice,
     betAmount ?? 0
   )
-  const shares = calculateShares(contract.pool, betAmount ?? 0, betChoice)
 
-  const estimatedWinnings = Math.floor(shares)
+  const shares = calculateShares(
+    contract.totalShares,
+    betAmount ?? 0,
+    betChoice
+  )
+
+  const estimatedWinnings = calculateEstimatedWinnings(
+    contract.totalShares,
+    shares,
+    betChoice
+  )
+
   const estimatedReturn = betAmount
     ? (estimatedWinnings - betAmount) / betAmount
     : 0
+
   const estimatedReturnPercent = (estimatedReturn * 100).toFixed() + '%'
 
   return (
diff --git a/web/lib/firebase/init.ts b/web/lib/firebase/init.ts
index 98734946..ba10545a 100644
--- a/web/lib/firebase/init.ts
+++ b/web/lib/firebase/init.ts
@@ -2,8 +2,8 @@ import { getFirestore } from '@firebase/firestore'
 import { initializeApp } from 'firebase/app'
 
 // TODO: Reenable this when we have a way to set the Firebase db in dev
-// export const isProd = process.env.NODE_ENV === 'production'
-export const isProd = true
+export const isProd = process.env.NODE_ENV === 'production'
+// export const isProd = true
 
 const firebaseConfig = isProd
   ? {