A property is negatively geared when the costs of owning it, mostly loan interest, exceed the rent it earns. The shortfall comes out of your pocket each week, and at tax time it can generally be deducted against your other income.
The strategy only works when the numbers work. The weekly cost has to be genuinely affordable through rate rises and vacancies, and the property has to be one you would want to hold long enough for growth to outrun the shortfall.
The calculator below gives you the honest first pass: pre-tax cash flow, then the estimated position after the deduction at your marginal rate.

