Interest-Only Mortgage Calculator Singapore 2026
IO Period Payment, Payment Shock After IO Ends & Rental Yield Break-Even
Compare interest-only (IO) vs standard amortizing mortgages for Singapore investment property loans. During the IO period, you pay only interest — no principal reduction — resulting in lower monthly payments. But when the IO period ends, the full principal must be repaid over the remaining tenure, creating a significant payment shock. This calculator shows your IO monthly payment, the amortizing payment after IO ends, the payment increase percentage, total interest cost comparison vs a standard loan, and whether your rental yield covers the IO and post-IO payments.
During the IO period, you pay interest only (no principal). After the IO period ends, the full loan amount is amortized over the remaining tenure. Example: 3yr IO + 25yr total = 22yr amortization period after IO.
Enter the expected gross rental yield on the property value (equal to loan amount for simplicity). The calculator checks whether rental income covers the IO payment and the post-IO amortizing payment. Leave blank to skip. Typical SG rental yields: 2.5%–4.5% depending on location and property type.
Enter your loan amount, rate, IO period, and total tenure to compare interest-only vs standard amortizing payments, see the payment shock, and check rental yield cashflow.
Interest-Only Mortgage Singapore 2026 — How IO Investment Loans Work, Payment Shock & When They Make Sense
An interest-only (IO) mortgage allows you to pay only the interest portion of your loan for an initial period (typically 2–5 years), without repaying any principal. This results in significantly lower monthly payments during the IO period — often 40–60% less than a standard amortizing loan. However, since no principal is repaid during IO, the full loan balance remains unchanged. When the IO period ends, the entire principal must be repaid over the remaining tenure, causing a sharp increase in monthly payments (the “payment shock”). IO mortgages are primarily used by property investors in Singapore who want to minimise initial cash outflow while collecting rental income, and by buyers who expect property values to appreciate during the IO period.
IO vs Standard Amortizing: Key Differences
| Feature | Interest-Only | Standard Amortizing |
|---|---|---|
| Monthly during initial period | Lower (interest only) | Higher (P + I) |
| Principal repaid during IO | S$0 | Gradually increasing |
| Payment after IO ends | Sharp increase | Stays the same |
| Total interest over life | Higher | Lower |
| Best for | Investors, short-hold | Owner-occupiers, long-hold |
| Availability in SG | Limited (investment only) | All property types |
How This IO Calculator Works — IO Payment, Shock Analysis & Rental Cashflow
Step 1 — Enter Loan and IO Structure
Enter loan amount, interest rate, the IO period (1–5 years), and the total loan tenure. The calculator computes the monthly interest-only payment during the IO period (loan × rate / 12) and the amortizing payment for the remaining tenure (standard P+I calculation on the full principal).
Step 2 — See the Payment Shock
The payment shock box shows the increase in monthly payment when IO ends — both in absolute dollars and as a percentage. A 3-year IO on a 25-year loan means the full principal is amortized over 22 years (instead of 25), resulting in higher post-IO payments than a standard 25-year amortizing loan. This shock can be 40–80% above the IO payment.
Step 3 — Compare Total Cost and Check Rental Yield
The total cost section compares IO mortgage total interest vs standard amortizing total interest — showing the extra interest cost of choosing IO. The optional rental yield check shows whether your gross rental income covers the IO payment (usually yes) and the post-IO amortizing payment (often no, creating negative cashflow). This helps investors decide whether IO makes financial sense for their strategy.
3 Real Singapore IO Examples — Investment Condo, Short-Hold Flip & Negative Yield Trap
S$1M Condo, 3yr IO at 3.5%
S$600K, 2yr IO, Sell in 3yr
S$1.5M, 5yr IO at 4%, Low Yield
3 Expert IO Tips — The Flip Strategy, Yield Requirement & TDSR Impact
IO Works Best for Short-Hold Investment Strategies
Interest-only mortgages are most effective when you plan to sell the property within or shortly after the IO period. The strategy: buy with IO to minimise monthly outflow, collect rental income during the holding period, then sell before the amortizing payments begin. Your profit comes from capital appreciation, not rental cashflow. This works well in rising markets but carries significant risk if property values decline or you cannot sell within the IO window. Remember: if you sell within 3 years of purchase, Seller’s Stamp Duty (SSD) applies (12%/8%/4%), which can eliminate your capital gain. Plan the holding period carefully around both the IO expiry and the SSD window.
Your Rental Yield Must Exceed the IO Rate for Positive Cashflow
During the IO period, your monthly payment = loan × rate / 12. For the rental to cover this, the gross rental yield must equal or exceed the interest rate. At 3.5% interest, you need at least 3.5% gross yield. But gross yield does not account for: (1) property tax (10%–20% for non-owner-occupied); (2) management fees (S$200–S$600/month for condos); (3) maintenance; (4) vacancy periods. Your net yield after these deductions is typically 1.0%–1.5% lower than gross. If gross yield = 3.5% and interest = 3.5%, your net cashflow is likely negative by S$500–S$1,000/month after expenses. Budget for this negative cashflow from other income sources.
TDSR Assessment Includes the Full Amortizing Payment, Not IO
When banks assess TDSR for an IO loan, they do not use the low IO payment. They assess at the full amortizing payment (at the stress-test rate of 4% for variable loans), calculated over the remaining tenure after IO. This means an IO loan does not give you more TDSR headroom than a standard loan — the bank ensures you can afford the post-IO payments, not just the IO payments. This is a common misconception: buyers who take IO thinking it will help them qualify for a larger loan are disappointed when the bank assesses at the higher amortizing amount. The IO feature reduces your actual cash outflow but does not increase your approved loan quantum.