Car Price-to-Income Ratio: A Transparent Affordability Measure
Calculate a simple individual income ratio, understand what it leaves out, and build the cash-flow checks needed for a real buying decision.
A car price-to-income ratio is a simple comparison of scale. To make it meaningful, state exactly which car price and income measure it uses. COEkaki does not have a verified quarterly affordability-index series established by the earlier article.
The formula
Months of income = complete car purchase price ÷ gross monthly individual income. For hypothetical inputs of $180,000 and $6,000, the result is thirty months. Expressed against annual income, $180,000 ÷ $72,000 = 2.5 years.
This is a worked example, not a measured median for Singapore. It does not mean the buyer needs only thirty months to save for the car: taxes, CPF and ordinary living expenses have not been deducted.
Use the same definition over time
A trend needs a consistent vehicle or documented vehicle basket, dated final prices and the same income population. Changing from individual to household income or from a full package to COE alone breaks comparability.
Median household income cannot simply be divided by two to obtain median individual income. The population, number of earners and statistical relationship are different.
Separate price and financing
A longer loan can reduce a monthly instalment without reducing the purchase-price ratio. It may increase total interest. A complete affordability assessment also needs the deposit, approved term, effective borrowing cost and the household’s remaining cash reserve.
Add ownership and exit costs
Insurance, road tax, energy, parking, repairs and disposal value affect the cost of using the car. The price-to-income ratio leaves them out. It also cannot value the convenience of trips the household needs the car to serve.
How a future measured series should work
Publish the input sources, dates, vehicle selection and calculation. Keep observed data separate from assumptions, preserve historical versions and show the effect of changing the basket. Avoid arbitrary labels such as “affordable below thirty” unless the threshold has a defensible purpose.
Earlier claims that COE explained a fixed percentage of index changes were not supported by an identified dataset or attribution method and have been removed. Readers can use the explicit ratio above while relying on their own cash-flow budget for the purchase decision.
Sources and review date
Reviewed on 13 September 2026. Historical results retain their exercise dates; worked budgets are assumptions, not quotations.