Which Calculator Should You Actually Use?

Open the calculators page on almost any property website and you will find the same problem: too many tools, not enough guidance on which one is actually relevant to you right now. Ours has twelve. That is not because every homeowner needs twelve answers - it is because different households, at different stages, need different questions answered, and cramming them into one generic “property calculator” usually produces a number nobody can quite trust.

This article is a map, not a manual. It will not walk you through how to use every field in every tool - each calculator does that itself. What it will do is help you work out which two or three actually matter for your situation, and in what order to use them.

It helps to think of the twelve tools less as a menu and more as a toolbox organised by trade. A plumber does not carry every tool for every job on every visit - they bring the two or three that fit the specific pipe in front of them. The sections below are organised the same way: by the situation you are actually in, not by an alphabetical list of features.

Why twelve calculators, not one

A single “how much is my property worth” box is easy to build and easy to use, which is exactly why so many property websites stop there. It is also close to useless for most of the actual decisions homeowners are trying to make. Whether you can sell your flat, what you can afford next, what your current loan is actually costing you, and whether decoupling makes financial sense are four entirely different calculations, each with its own inputs and its own regulatory rules behind it. Splitting them into separate, purpose-built tools means each one can ask you the right questions - and only the right questions - instead of forcing every homeowner through the same generic form.

It also means each calculator can be built and reviewed against the specific rules that actually govern it - HDB's conditions for one, MAS's TDSR and MSR limits for another, IRAS's stamp duty schedule for a third - rather than a single set of assumptions stretched to loosely cover every scenario. That specificity is what lets each tool stay accurate as the underlying rules are reviewed and updated over time.

There is a cost to this approach too, and it is worth naming honestly: twelve separate tools can look intimidating on a page, especially to someone who just wants a quick answer. That is exactly the gap this article is meant to close - not by simplifying the tools themselves, but by making it obvious, in plain language, which ones apply to you and which ones do not.

If you are not sure whether to move at all

MOP / SSD Checker

This is almost always the right place to start, and it is deliberately the first tab on our calculators page. Before any conversation about selling, upgrading or holding goes further, it helps to know exactly where your flat stands: whether your Minimum Occupation Period has been fulfilled, and whether a Seller's Stamp Duty holding period still applies if you bought a private property more recently. Getting this milestone wrong - assuming you are free to sell when you are not, or assuming SSD applies when it no longer does - derails every other number that follows.

This tool is deliberately conservative: it gives you an indicative milestone based on the dates and property type you enter, and reminds you to confirm the exact date with HDB or the relevant authority before acting on it. That caution is intentional. MOP and SSD dates can shift for reasons that are easy to overlook - an occupation history that was not entirely straightforward, or a purchase completed earlier or later than originally projected - and a wrong assumption here is the single most expensive mistake a household can make before they have even started planning their next move.

Property Stagnation Calculator

This one answers a quieter but equally important question: what is it actually costing you to keep holding a property you have been meaning to sell for a while? It weighs ongoing loan interest, opportunity cost and other holding costs against the price movement you would need just to break even. Households who have been putting off a decision “until the market improves” often find this calculator gives their hesitation an actual number to react to, one way or the other.

If you are weighing what you can afford

Affordability Calculator

This tool takes your income and existing commitments and returns two figures worth distinguishing carefully: a maximum bank-approved purchase price, and a more sustainable figure based on a comfortable monthly instalment rather than the regulatory ceiling. If you read nothing else on this page, read the distinction between those two numbers - it is the single most common source of financial stress in the years after a property purchase.

Reverse Affordability Calculator

Sometimes the more useful question runs the other way: you already have a specific property or price range in mind, and want to know roughly what income or savings profile it would typically require. This calculator works backwards from a target price to give you that reference point, which is particularly useful early in a search, before you have firmed up your own budget.

Eligibility Checker

Once you have a specific loan amount in mind, this checker tests it directly against the Loan-to-Value limit, Total Debt Servicing Ratio and Mortgage Servicing Ratio (where applicable) that would actually apply to your purchase. It is the most literal, most regulatory of the three affordability tools - useful once you are close to making an offer and want to confirm a specific number will actually clear the bank's checks.

If you are looking at your current loan

Mortgage Repayment Calculator

A straightforward, essential tool: enter a loan amount, rate and tenure, and see the monthly instalment, total interest and total cost over the life of the loan. Useful when comparing package offers, or simply understanding what a given loan size actually commits you to every month.

Refinance Savings Calculator

If your mortgage lock-in period is ending, or you suspect your current rate is no longer competitive, this calculator compares your existing rate against a new one and estimates how long it would take to recover any switching costs. It is the practical companion to the decision between repricing with your current bank and refinancing elsewhere.

If you are planning an actual sale

Sale Proceeds Calculator

This is the calculator most homeowners eventually reach for, and for good reason: it estimates your net cash proceeds after your outstanding loan, CPF refund (principal plus accrued interest), and legal and agency costs are all deducted from your expected selling price. Selling price and cash in hand are two different numbers, and this tool exists specifically to show you the gap between them before you plan a next purchase around the wrong one.

Stamp Duty Calculator

Whether you are buying your next property or simply want to understand the cost structure of a purchase you are considering, this tool estimates Buyer's Stamp Duty and, where relevant, Additional Buyer's Stamp Duty based on your buyer profile and how many properties you already own. It is worth running early in your planning, since stamp duty is payable soon after signing and is easy to underestimate.

If your household situation is more complex

The remaining three tools are genuinely useful, but only for households in specific situations - most homeowners will never need any of them, and that is fine. If none of the three below sound like your situation, you can safely skip this section entirely and move on to the reference table.

Decoupling Calculator

For couples where one party wants to transfer their share of an existing property to the other, in order to free up the second party to buy a next property without Additional Buyer's Stamp Duty exposure, this tool weighs the transfer costs (stamp duty on the share transferred, legal fees) against the ABSD that decoupling would help avoid. It is a genuinely complex, situation-specific decision, and this calculator is meant as a starting estimate, not a substitute for advice from a qualified conveyancing lawyer.

Sell One, Buy Two Calculator

Some households, often at a point of family growth or a shift towards holding property for the next generation, consider selling a single property to fund two smaller purchases. This tool estimates the combined costs and stamp duties involved in that kind of restructuring, which is easy to underestimate when mentally comparing only the purchase prices involved.

Buy First or Sell First Comparison

This tool puts the two sequencing strategies side by side for your own numbers, rather than as a general discussion - useful once you have decided you are moving and are genuinely undecided about which order to run the transactions in. It works best once you have already run the Sale Proceeds and Affordability calculators, since the sequencing comparison is only as useful as the funding figures feeding into it.

A quick reference table

How the calculators actually connect

For the most common journey - a household past MOP, weighing whether to sell, upgrade, right-size or hold - the tools above are rarely used in isolation. They tend to follow a natural sequence, each one feeding the next:

1. Confirm your milestone with the MOP / SSD Checker, so you know what is actually available to you.
2. Estimate your net Sale Proceeds, so you are working from real cash figures rather than a hoped-for selling price.
3. Check what you could comfortably afford next with the Affordability Calculator, using those proceeds as your starting point.
4. Run the Eligibility Checker once you have a specific loan amount in mind, to confirm it against TDSR, MSR and LTV limits.
5. Estimate the Stamp Duty on your intended purchase, so your total funding need is complete, not just the purchase price.
6. If sequencing is still undecided at this point, use the Buy First or Sell First Comparison to weigh the trade-offs against your own numbers.

Notice what is missing from that sequence for most households: decoupling and Sell One, Buy Two. Those two exist specifically for less common situations, and pulling them into a standard MOP decision usually adds complexity without adding clarity.

What none of them can tell you

Every calculator on this page does one thing well: it turns a set of inputs into a specific number, calculated consistently and transparently. None of them can tell you whether now is the right time for your household, whether a smaller home would actually suit your lifestyle better than you assume, or how much certainty your family needs relative to how much convenience you are willing to trade for it. Those are judgment calls, informed by the numbers but not decided by them.

There is also a limit to what any calculator can do with inputs it does not have. Every tool on this page works from the figures you enter - your income, your outstanding loan, your CPF balance, your assumptions about a future selling price. If those inputs are optimistic, the output will be too, no matter how carefully the underlying formula is built. The single best way to get a genuinely useful number out of any of these tools is to start with conservative, verified figures - your actual CPF statement rather than a rough guess, a recent transacted price rather than an asking price - rather than the most hopeful version of each input.

Final perspective

You do not need to work through all twelve calculators to make a good decision. Most households need two or three, used in the right order, to turn a vague sense of “we should probably look into this” into a set of real, specific figures. Start with your milestone, move to your proceeds and affordability, and only reach for the more specialised tools if your situation actually calls for them.

If you are genuinely unsure which two or three apply to you, that uncertainty is itself useful information - it usually means your situation has a wrinkle a generic calculator page cannot fully anticipate. That is precisely the kind of conversation worth having with someone who works through these numbers for a living, rather than guessing at which tab to click next.

This article provides general information and does not constitute legal, tax or financial advice. Property policies and eligibility criteria may change. Check the latest requirements with the relevant authorities or seek professional advice for your circumstances.

Amanda Yap

Co-Founder, MOP Freedom · Property & Mortgage Strategist

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