Irish Calculators
Saving & investing

Portfolio Rebalancing Trade Calculator

Enter current asset values and target weights to see the trades needed for rebalancing. You choose the allocation, and the calculation does not optimise tax or restrict trades to purchases.

Runs privately in your browserMethod reviewed

Your numbers

One row per asset. Target weights must total 100%. Include cash as an asset if it should remain invested as cash.
Display currency only. Convert all inputs to this currency before calculation.
Your figures stay on this device.

How the calculation works

Rebalancing compares what you currently hold with what you would hold at chosen target percentages. This tool calculates the money to buy or sell after a cash addition or withdrawal and a separate reserve for dealing costs.

Target value = (current total + cash flow − cost reserve) × target weight. Trade = target value − current value.

  1. Find investable capital

    Add the current holding values and the external cash flow, then subtract the dealing-cost reserve. A withdrawal therefore reduces the amount distributed across targets.

  2. Apply target percentages

    Each target percentage is multiplied by investable capital. Percentages must add to 100%, so every unit of capital is assigned to a stated asset.

  3. Compare target and current holdings

    A positive difference is a purchase and a negative difference is a sale. The separate trade totals help reconcile the proposed activity with external cash and costs.

Worked example: Check Total purchases

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example holds 600 in A and 400 in B with equal targets. The target is 500 each, requiring a sale of 100 from A and a purchase of 100 in B; total purchases are 100.

Asset name, current value, target %
A,600,50 B,400,50
New cash added (negative for withdrawal)
0
Cash reserved for all dealing costs
0
Currency for all amounts
Euro (EUR)

Expected result

Total purchases
€100.00
Worked example: Check Total purchases

Sample inputs demonstrate the method. They are not a forecast or product offer.

Asset name, current value, target %
A,600,50 B,400,50
New cash added (negative for withdrawal)
200
Cash reserved for all dealing costs
0
Currency for all amounts
Euro (EUR)

Expected result

Total purchases
€200.00

Understanding your result

The amounts are value-based trades, not executable orders in whole shares. Prices, minimum order sizes and settlement requirements must be considered separately.

Target weights are supplied choices. The tool does not select a portfolio, minimise capital-gains tax or guarantee that rebalancing can be achieved with purchases alone.

Questions you might have

What does the result include?

Translate current asset values and target percentages into purchases and sales after a cash addition or withdrawal.

Which limits should I check?

Target weights are chosen by you; no recommended asset allocation is supplied.

Choosing the right inputs

Asset name, current value, target %
Enter current market values, not original purchase costs. Include cash as its own asset if part of the target portfolio should remain in cash.
New cash added (negative for withdrawal)
Use positive amounts for new cash and negative amounts for a withdrawal. Do not include the same new money in current asset values.
Cash reserved for all dealing costs
Reserve the total cash expected to cover dealing costs. This reduces the capital available for target holdings before trades are calculated.

Common mistakes to avoid

  • Do not enter percentage weights as decimals such as 0.5 when you mean 50%.
  • Do not add the dealing-cost reserve to individual asset values as well.

Assumptions to check

  • Target weights are chosen by you; no recommended asset allocation is supplied.
  • All calculations run on your device. Figures are scenarios based on your inputs, not investment recommendations.

Sources and method

Read our calculation and testing approach.