diff --git a/backend/app/api/portfolio.py b/backend/app/api/portfolio.py
index 2c01e38..5eae1c5 100644
--- a/backend/app/api/portfolio.py
+++ b/backend/app/api/portfolio.py
@@ -14,7 +14,9 @@ from app.schemas.portfolio import (
     TargetCreate, TargetResponse,
     HoldingCreate, HoldingResponse,
     TransactionCreate, TransactionResponse,
+    RebalanceResponse, RebalanceSimulationRequest, RebalanceSimulationResponse,
 )
+from app.services.rebalance import RebalanceService
 
 router = APIRouter(prefix="/api/portfolios", tags=["portfolios"])
 
@@ -289,3 +291,28 @@ async def add_transaction(
     db.commit()
     db.refresh(transaction)
     return transaction
+
+
+@router.get("/{portfolio_id}/rebalance", response_model=RebalanceResponse)
+async def calculate_rebalance(
+    portfolio_id: int,
+    current_user: CurrentUser,
+    db: Session = Depends(get_db),
+):
+    """Calculate rebalancing for a portfolio."""
+    portfolio = _get_portfolio(db, portfolio_id, current_user.id)
+    service = RebalanceService(db)
+    return service.calculate_rebalance(portfolio)
+
+
+@router.post("/{portfolio_id}/rebalance/simulate", response_model=RebalanceSimulationResponse)
+async def simulate_rebalance(
+    portfolio_id: int,
+    data: RebalanceSimulationRequest,
+    current_user: CurrentUser,
+    db: Session = Depends(get_db),
+):
+    """Simulate rebalancing with additional investment amount."""
+    portfolio = _get_portfolio(db, portfolio_id, current_user.id)
+    service = RebalanceService(db)
+    return service.calculate_rebalance(portfolio, additional_amount=data.additional_amount)