Visualise how monthly payments change across different interest rates and loan tenures.
How to Use the Heatmap Calculator
Key Takeaways
The heatmap shows every combination of interest rate and tenure simultaneously — identify your affordable zone (green cells) before you talk to a bank.
Find your stress-test boundary: the cell at 4% (MAS stress-test floor) + your intended tenure is your bank's actual approval limit, not the current market rate.
A 5-year tenure reduction (e.g., 30→25 years) typically increases monthly payments by 8–12% but saves substantially more in total interest over the loan life.
Your comfortable payment range is more important than the minimum possible payment — find the tenure/rate combination you can sustain at the 75th percentile of your budget.
What It Does
What happens if interest rates jump to 4.5%? Or if you shorten your loan to 20 years? The Borrowing Sensitivity Heatmap shows you at a glance how every combination of interest rate and loan tenure affects your monthly payment. Stress-test your mortgage before you commit.
You can find this calculator in the Calculators tab on ShiokNest. It updates results instantly as you adjust inputs — no waiting, no page reloads.
Why It Matters
Interest rates are cyclical. They go up, and they come down. The heatmap prepares you for every scenario so you are never caught off guard. It matters because:
How It Works
Navigate to Calculators — Click the "Calculators" tab in the ShiokNest navigation bar. All 26 calculators are grouped by purpose for easy access.
Select the calculator — Choose "How to Read the Borrowing Sensitivity Heatmap" from the calculator list. You will see default values already loaded so you can explore immediately.
️ Enter your values — Replace the defaults with your own numbers. The key fields are:
Review the results — The calculator updates instantly as you change any input. A colour-coded grid shows monthly payments across every rate/tenure combination. Green cells are affordable, red cells exceed your target payment.
Run what-if scenarios — This is where the real power lies. Change one variable at a time to see its impact. For example, try increasing the interest rate by 1% or extending your holding period by 5 years. Note how the results shift.
Compare and decide — Run 2-3 different scenarios and note the results. This gives you a range of outcomes to base your decision on, rather than relying on a single projection.
Examples
$1.2M loan: mapping the affordable zone across rates and tenures
Inputs
Loan amount
$1,200,000
Rate range
2.5% – 5.0% (in 0.5% steps)
Tenure range
15 – 30 years
Monthly budget ceiling
$5,500
Results
Current rate (3.5%), 25yr
$5,993/month — just above budget
Current rate (3.5%), 30yr
$5,391/month — within budget
Stress-test (4%), 25yr
$6,322/month — bank assessment rate
Safe zone
Rate ≤3.5% AND tenure ≥ 28yr, or Rate ≤3.0% AND tenure ≥ 25yr
How to read this:
The heatmap immediately shows that at $1.2M and a $5,500 ceiling, the buyer is on the edge at current rates. The green/red boundary runs diagonally across the grid — cells to the bottom-right (longer tenure, lower rate) are affordable; cells to the top-left are not. The critical insight: the 25-year tenure fails the budget at today's 3.5% rate, pushing the buyer to 30 years. But at the stress-test rate of 4%, even 30 years costs $6,053/month — above budget. This tells the buyer they are a...
Rate risk mapping: how much does a 1.5% rate rise hurt?
Inputs
Loan amount
$900,000
Current rate
2.8% (SORA-linked at trough)
Tenure
25 years (fixed)
Question
What does a 1.5% rate rise cost per month?
Results
At 2.8%, 25yr
$4,163/month
At 4.3% (+1.5%), 25yr
$4,898/month
Monthly increase
+$735/month (+17.6%)
Annual additional cost
+$8,820/year
How to read this:
A 1.5% SORA rise adds $735/month to this mortgage — $8,820/year that was not in the original budget. The heatmap makes this visible by highlighting the cell at 4.3%/25yr versus 2.8%/25yr. For a buyer whose comfortable ceiling is $4,500/month, a 1.5% rate rise pushes them $400 above their limit — not catastrophic, but requiring a budget adjustment. The heatmap lets the buyer pre-plan this scenario: if rates rise to 4.3%, they know they need to cut $700/month from other expenses, or they ha...
Tips & Pitfalls
Expert Tips
Use realistic assumptions — Singapore condo appreciation has historically averaged 2-4% per year. Avoid overly optimistic projections. When in doubt, use 3% as a baseline.
Find your comfort zone — Identify the range of payments you can comfortably afford, then look at which rate/tenure combinations keep you within that range.
Prepare for rate rises — If you are comfortable at 3.5%, make sure you can also survive at 4.5%. SORA-linked rates can move quickly.
Common Pitfalls
Assuming rates stay constant — The heatmap shows snapshots, but your actual rate will change over time. Focus on the range you can tolerate, not a single cell.
Frequently Asked Questions
Is my data saved?
No. All calculations run entirely in your browser. Nothing is stored on our servers or shared with third parties.
What rate range should I use?
Set the minimum at the current SORA-linked rate (check MAS.gov.sg for the latest 3-month compounded SORA, then add the typical bank spread of 0.8–1.0%). Set the maximum at 5.5% — this covers the highest Singapore mortgage rates seen in the past 15 years and represents a realistic worst-case stress scenario.
Can I save my results?
Log in to save scenarios to your dashboard, or use the share button to copy a URL that encodes your inputs.
Why is the 4% cell highlighted?
MAS requires banks to assess TDSR affordability at a floor rate of 4% for private property, regardless of the current market rate. The calculator highlights this cell so you can see what your bank considers your maximum serviceable payment — the actual benchmark your loan approval is assessed against.