Methodology

All HDB resale transaction data on CheckHowMuch is sourced from data.gov.sg, Singapore's official open data platform, published by the Housing and Development Board (HDB) under the Singapore Open Data Licence.

Each transaction record contains: month, town, flat type, block number, street name, storey range, floor area (sqm), flat model, lease commencement date, remaining lease, and resale price. Resale prices in the dataset range from approximately $140,000 (older 2-room flats) to over $1,000,000 (premium flats in mature estates). CheckHowMuch does not modify, interpolate, or estimate any source data. All values shown in transaction tables are exactly as published by HDB.

Property valuations on CheckHowMuch use Bala's Table, the Singapore Land Authority's (SLA) official leasehold relativity model. Bala's Table was established in 1948 and is used by the Singapore government for leasehold property compensation calculations, including compulsory land acquisitions under the Land Acquisition Act.

The model calculates the value of a leasehold interest as a proportion of freehold value. The core formula is:

The discount rate of 3.5% is the rate specified in the original Bala's Table as adopted by SLA. This rate determines how quickly the leasehold value depreciates relative to freehold.

The non-linear nature of the curve is significant: decay is gradual above 50 years but accelerates sharply below 40 years. This is why HDB flats with very long leases (80+ years) experience minimal annual depreciation, while flats approaching 30-40 years remaining see measurably faster value erosion.

The annual lease decay percentage shown on each block page represents the proportion of leasehold value lost per year at the current remaining lease. It is calculated by comparing the Bala ratio at the current lease with the ratio one year shorter:

For a block with 55 years remaining, the annual lease decay is approximately 0.66%. For a block with 30 years remaining, it accelerates to approximately 1.34%. At 15 years, it reaches 2.51%.

The lease bar visualisation on each block page shows the remaining lease as a proportion of the original 99 years, with the annual decay rate displayed alongside. This provides an at-a-glance assessment of where a block sits on the depreciation curve.

The "What's Your Unit Worth?" valuation tool estimates current market value using comparable recent transactions. The comparable set is defined as:

• Same town as the target block (e.g. all of Ang Mo Kio)
• Same flat type as selected by the user (e.g. 4-Room)
• Last 12 months of recorded transactions

The estimated value is the median price of the comparable set. Median is used rather than mean to reduce the influence of outlier transactions (e.g. unusually high or low-floor units, recently renovated flats, or distressed sales).

All comparables are pre-computed at build time from the full data.gov.sg dataset. There are no live API calls when a user clicks "Get Estimate". The comparable count displayed (e.g. "Based on 283 comparable sales") reflects the total matching transactions in the last 12 months for that town and flat type.

The projection tool estimates what a flat might be worth in future years by combining market appreciation with lease decay:

The 3% annual appreciation rate reflects long-term sustainable HDB resale price growth in Singapore. This is a modelling assumption, not a guarantee. Actual appreciation varies by location, market conditions, government policy (cooling measures, grants), and individual block factors.

The projection explicitly accounts for lease decay through the Bala ratio adjustment. For newer flats with 80+ years remaining, the lease decay component is negligible (~0.18%/year). For older flats approaching 40 years, the lease decay partially or fully offsets market appreciation, which the projection reflects.

CheckHowMuch's data pipeline runs on an automated schedule:

The twice-monthly fetch ensures we capture data.gov.sg updates regardless of whether HDB publishes early or late in the month. When the source data has not changed, the hash check prevents unnecessary rebuilds.

• Storey range, not unit number. HDB publishes transactions in 3-storey bands (e.g. "07 TO 09"), not exact unit numbers. This means we cannot provide unit-level precision.
• 1-2 month data lag. Transactions appear on data.gov.sg weeks after completion. More recent sales may not yet be reflected.
• No renovation or condition data. The dataset does not include information about flat condition, renovations, or special features that affect price.
• Comparables are town-wide. The valuation uses all comparable sales in the same town, not just the immediate neighbourhood. Micro-location factors (proximity to MRT, schools, amenities) are not weighted.
• 3% appreciation is an assumption. The projection model uses 3% annual appreciation as a long-term baseline. Actual market performance may differ significantly due to government policy changes, economic conditions, or location-specific factors.
• Bala's Table is a theoretical model. While it is the SLA's official model, actual market prices for short-lease flats may deviate from the theoretical curve due to CPF restrictions, bank loan limitations, and buyer sentiment.
• Not financial advice. CheckHowMuch provides data and estimates for informational purposes only. Users should consult qualified property valuers and financial advisers before making property decisions.