Getting the Most From a Share Profit Calculator: Tips and Common Errors

Updated 13 August 2026 · Savings and investing

A Share Profit Calculator gives a fast answer, but the answer is only as good as what goes in. These are the mistakes we see most often with share profit calculations in Australia, and how to avoid them.

1. Forgetting tax on returns

Interest is taxed at your marginal rate, so a 5% account may return closer to 3.4% after tax.

2. Ignoring inflation

A return below inflation means your money buys less over time.

3. Comparing total rather than annual returns

Always convert returns to a yearly rate before comparing investments held for different periods.

4. Chasing bonus rates without meeting conditions

Missing a deposit or making a withdrawal can drop a bonus saver to its low base rate.

5. Overlooking the detail that matters most here

Profit on shares is a capital gain. Holding for more than 12 months can halve the taxable amount.

How the net profit changes with sell price per share

A common mistake is getting one input slightly wrong. Here is what happens to the net profit when “Sell price per share ($)” is off by up to 20% in either direction, with everything else held steady.

Sell price per share ($)	Net profit
10	-$20.00
11.25	$1,230.00
12.5	$2,480.00
13.75	$3,730.00
15	$4,980.00

At 10 the result is -$20.00; at 15 it is $4,980.00. If a small change in this input moves the answer a lot, it is worth double-checking that figure before you rely on the result.

A quick sense check

Profit = sell value − buy value − brokerage on both trades. With typical inputs the calculator returns net profit of $2,480.00. If your own result looks wildly different, check that each figure is in the right unit and period (weekly, monthly or yearly) before drawing conclusions.