diff --git a/api/routers/contest_records.py b/api/routers/contest_records.py
index b02f433..e7a519c 100644
--- a/api/routers/contest_records.py
+++ b/api/routers/contest_records.py
@@ -129,6 +129,7 @@ async def contest_records_user(
 class QueryOfPredictedRating(BaseModel):
     contest_name: str
     users: conlist(UserKey, min_length=1, max_length=26)
+    hypothetical_entries: Optional[List[UserKey]] = None
 
 
 class ResultOfPredictedRating(BaseModel):
@@ -158,7 +159,22 @@ async def predicted_rating(
         )
         for user in query.users
     )
-    return await asyncio.gather(*tasks)
+    results = await asyncio.gather(*tasks)
+
+    if query.hypothetical_entries:
+        hypothetical_tasks = (
+            ContestRecordPredict.find_one(
+                ContestRecordPredict.contest_name == query.contest_name,
+                ContestRecordPredict.data_region == entry.data_region,
+                ContestRecordPredict.username == entry.username,
+                projection_model=ResultOfPredictedRating,
+            )
+            for entry in query.hypothetical_entries
+        )
+        hypothetical_results = await asyncio.gather(*hypothetical_tasks)
+        results.extend(hypothetical_results)
+
+    return results
 
 
 class QueryOfRealTimeRank(BaseModel):
@@ -188,3 +204,57 @@ async def real_time_rank(
         ContestRecordArchive.username == query.user.username,
         projection_model=ResultOfRealTimeRank,
     )
+
+
+class HypotheticalEntry(BaseModel):
+    contest_name: str
+    username: str
+    data_region: str
+    rank: int
+    score: int
+    finish_time: datetime
+
+
+class HypotheticalRatingChange(BaseModel):
+    old_rating: float
+    new_rating: float
+    delta_rating: float
+
+
+@router.post("/hypothetical-entry")
+async def hypothetical_entry(
+    request: Request,
+    entry: HypotheticalEntry,
+) -> HypotheticalRatingChange:
+    """
+    Calculate rating change based on a hypothetical entry.
+    :param request:
+    :param entry:
+    :return:
+    """
+    await check_contest_name(entry.contest_name)
+
+    # Fetch the user's current rating and attended contests count
+    user = await User.find_one(
+        User.username == entry.username,
+        User.data_region == entry.data_region,
+    )
+
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+
+    old_rating = user.rating
+    attended_contests_count = user.attendedContestsCount
+
+    # Calculate the new rating based on the hypothetical entry
+    rank_array = np.array([entry.rank])
+    rating_array = np.array([old_rating])
+    k_array = np.array([attended_contests_count])
+    delta_rating_array = elo_delta(rank_array, rating_array, k_array)
+    new_rating = old_rating + delta_rating_array[0]
+
+    return HypotheticalRatingChange(
+        old_rating=old_rating,
+        new_rating=new_rating,
+        delta_rating=delta_rating_array[0],
+    )
diff --git a/client/src/pages/Predicted/PredictedContests.jsx b/client/src/pages/Predicted/PredictedContests.jsx
index 805f31d..4d38b44 100644
--- a/client/src/pages/Predicted/PredictedContests.jsx
+++ b/client/src/pages/Predicted/PredictedContests.jsx
@@ -1,4 +1,4 @@
-import { useEffect } from "react";
+import { useEffect, useState } from "react";
 import { Link, useParams } from "react-router-dom";
 
 import useSWR from "swr";
@@ -73,6 +73,118 @@ const ContestsTable = ({ contests }) => {
   );
 };
 
+const HypotheticalEntryForm = ({ titleSlug, setHypotheticalResult }) => {
+  const [username, setUsername] = useState("");
+  const [dataRegion, setDataRegion] = useState("US");
+  const [rank, setRank] = useState("");
+  const [score, setScore] = useState("");
+  const [finishTime, setFinishTime] = useState("");
+
+  const handleSubmit = async (e) => {
+    e.preventDefault();
+    const response = await fetch(`${baseUrl}/contest-records/hypothetical-entry`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        contest_name: titleSlug,
+        username,
+        data_region: dataRegion,
+        rank: parseInt(rank),
+        score: parseInt(score),
+        finish_time: new Date(finishTime).toISOString(),
+      }),
+    });
+    const result = await response.json();
+    setHypotheticalResult(result);
+  };
+
+  return (
+    <form onSubmit={handleSubmit} className="container mx-auto text-center">
+      <div className="form-control">
+        <label className="input-group">
+          <span>Username</span>
+          <input
+            type="text"
+            placeholder="Username"
+            className="input input-bordered"
+            value={username}
+            onChange={(e) => setUsername(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Data Region</span>
+          <select
+            className="select select-bordered"
+            value={dataRegion}
+            onChange={(e) => setDataRegion(e.target.value)}
+            required
+          >
+            <option value="US">US</option>
+            <option value="CN">CN</option>
+          </select>
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Rank</span>
+          <input
+            type="number"
+            placeholder="Rank"
+            className="input input-bordered"
+            value={rank}
+            onChange={(e) => setRank(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Score</span>
+          <input
+            type="number"
+            placeholder="Score"
+            className="input input-bordered"
+            value={score}
+            onChange={(e) => setScore(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Finish Time</span>
+          <input
+            type="datetime-local"
+            className="input input-bordered"
+            value={finishTime}
+            onChange={(e) => setFinishTime(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <button className="btn btn-primary" type="submit">
+        Calculate Hypothetical Rating Change
+      </button>
+    </form>
+  );
+};
+
+const HypotheticalResult = ({ result }) => {
+  if (!result) return null;
+
+  return (
+    <div className="container mx-auto text-center">
+      <h2>Hypothetical Rating Change</h2>
+      <p>Old Rating: {result.old_rating.toFixed(2)}</p>
+      <p>New Rating: {result.new_rating.toFixed(2)}</p>
+      <p>Delta Rating: {result.delta_rating.toFixed(2)}</p>
+    </div>
+  );
+};
+
 const PredictedContest = () => {
   useEffect(() => {
     document.title = "Predicted Contests";
@@ -101,6 +213,8 @@ const PredictedContest = () => {
   );
   // console.log(`totalCount=${totalCount} pageNum=${pageNum}`);
 
+  const [hypotheticalResult, setHypotheticalResult] = useState(null);
+
   if (!contests || isLoading)
     return (
       <div className="grid h-screen place-items-center ">
@@ -132,6 +246,11 @@ const PredictedContest = () => {
         pageURL={""}
         pageSize={pageSize}
       />
+      <HypotheticalEntryForm
+        titleSlug={contests[0].titleSlug}
+        setHypotheticalResult={setHypotheticalResult}
+      />
+      <HypotheticalResult result={hypotheticalResult} />
     </>
   );
 };
diff --git a/client/src/pages/Predicted/PredictedRecords.jsx b/client/src/pages/Predicted/PredictedRecords.jsx
index 4e4b3d2..95efe9a 100644
--- a/client/src/pages/Predicted/PredictedRecords.jsx
+++ b/client/src/pages/Predicted/PredictedRecords.jsx
@@ -168,6 +168,118 @@ const PredictedRecordsTable = ({ predictedRecords, setUser }) => {
   );
 };
 
+const HypotheticalEntryForm = ({ titleSlug, setHypotheticalResult }) => {
+  const [username, setUsername] = useState("");
+  const [dataRegion, setDataRegion] = useState("US");
+  const [rank, setRank] = useState("");
+  const [score, setScore] = useState("");
+  const [finishTime, setFinishTime] = useState("");
+
+  const handleSubmit = async (e) => {
+    e.preventDefault();
+    const response = await fetch(`${baseUrl}/contest-records/hypothetical-entry`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        contest_name: titleSlug,
+        username,
+        data_region: dataRegion,
+        rank: parseInt(rank),
+        score: parseInt(score),
+        finish_time: new Date(finishTime).toISOString(),
+      }),
+    });
+    const result = await response.json();
+    setHypotheticalResult(result);
+  };
+
+  return (
+    <form onSubmit={handleSubmit} className="container mx-auto text-center">
+      <div className="form-control">
+        <label className="input-group">
+          <span>Username</span>
+          <input
+            type="text"
+            placeholder="Username"
+            className="input input-bordered"
+            value={username}
+            onChange={(e) => setUsername(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Data Region</span>
+          <select
+            className="select select-bordered"
+            value={dataRegion}
+            onChange={(e) => setDataRegion(e.target.value)}
+            required
+          >
+            <option value="US">US</option>
+            <option value="CN">CN</option>
+          </select>
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Rank</span>
+          <input
+            type="number"
+            placeholder="Rank"
+            className="input input-bordered"
+            value={rank}
+            onChange={(e) => setRank(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Score</span>
+          <input
+            type="number"
+            placeholder="Score"
+            className="input input-bordered"
+            value={score}
+            onChange={(e) => setScore(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <div className="form-control">
+        <label className="input-group">
+          <span>Finish Time</span>
+          <input
+            type="datetime-local"
+            className="input input-bordered"
+            value={finishTime}
+            onChange={(e) => setFinishTime(e.target.value)}
+            required
+          />
+        </label>
+      </div>
+      <button className="btn btn-primary" type="submit">
+        Calculate Hypothetical Rating Change
+      </button>
+    </form>
+  );
+};
+
+const HypotheticalResult = ({ result }) => {
+  if (!result) return null;
+
+  return (
+    <div className="container mx-auto text-center">
+      <h2>Hypothetical Rating Change</h2>
+      <p>Old Rating: {result.old_rating.toFixed(2)}</p>
+      <p>New Rating: {result.new_rating.toFixed(2)}</p>
+      <p>Delta Rating: {result.delta_rating.toFixed(2)}</p>
+    </div>
+  );
+};
+
 const PredictedRecords = () => {
   const pageSize = 25; // hard code `pageSize` temporarily
 
@@ -178,6 +290,7 @@ const PredictedRecords = () => {
   const [predictedRecordsURL, setPredictedRecordsURL] = useState(null);
   const [isSearching, setIsSearching] = useState(false);
   const [user, setUser] = useState(null);
+  const [hypotheticalResult, setHypotheticalResult] = useState(null);
 
   useEffect(() => {
     document.title = `${titleSlug} 🔮`;
@@ -303,6 +416,12 @@ const PredictedRecords = () => {
         />
       )}
 
+      <HypotheticalEntryForm
+        titleSlug={titleSlug}
+        setHypotheticalResult={setHypotheticalResult}
+      />
+      <HypotheticalResult result={hypotheticalResult} />
+
       <input type="checkbox" id="my-modal-4" className="modal-toggle" />
       <label htmlFor="my-modal-4" className="modal cursor-pointer">
         <label className="modal-box relative" htmlFor="">