About the Portfolio Allocation Calculator
Check how your portfolio is split and what to buy or sell to get back to your target allocation. Enter each holding's current value and its target percentage, add any new cash, and see the current weights, the trades and the weights afterwards.
Tick the option to avoid selling and the page puts the new cash only into the holdings that are below target, which avoids the tax and fees of selling.
How it works
Each holding's weight is its value divided by the total. Its target value is the total after any new cash times its target percentage, and the trade is the difference: positive to buy, negative to sell.
With shares at 7,000 and bonds at 3,000 and a 50/50 target, the total is 10,000, so each should be 5,000: sell 2,000 of shares and buy 2,000 of bonds. Adding 1,000 of cash makes the target 5,500 each.
Without selling, the new cash goes to the holdings below target in proportion to how far below they are; if there is more cash than they need, the rest is spread by target. The tests check that a full rebalance always lands exactly on the targets and that the trades add up to the cash added.
Assumptions and limits
- Targets must add up to 100%.
- Values are in one currency; convert holdings in other currencies first.
- Trades are in money, not shares; round to whole shares when you place the orders.
Worked examples
Back to 50/50
Shares 7,000 and bonds 3,000 with a 50/50 target: sell 2,000 of shares and buy 2,000 of bonds.
With new cash
Adding 1,000: sell 1,500 of shares and buy 2,500 of bonds.
Without selling
With only 1,000 to add and no selling, all of it goes to bonds; with 5,000, 500 goes to shares and 4,500 to bonds.
How to use the Portfolio Allocation Calculator
- List your holdings. With their value now and target %.
- Add new cash. Optional, and choose whether to sell.
- Read the trades. What to buy or sell, and the result.
Frequently asked questions
How do I rebalance my portfolio?
Work out each holding's target value as the total portfolio times its target percentage, then buy or sell the difference from its current value. The page does this for every holding at once and shows the weights afterwards.
How often should I rebalance?
Many investors rebalance once or twice a year, or when a holding drifts more than about five percentage points from its target. Rebalancing too often adds fees and taxes, while never rebalancing lets the risk drift.
Can I rebalance without selling?
Yes. Direct new money into the holdings that are below their targets. Tick the no-selling option and the page splits your new cash between those holdings in proportion to how far below target they are.
What is a good asset allocation?
It depends on your goals, time horizon and tolerance for losses. Common examples are 60% shares and 40% bonds, or a larger share in shares for long horizons. This tool helps you keep to the allocation you choose.
Do the targets have to add up to 100%?
Yes, because they describe how the whole portfolio is divided. The page shows the running total of your targets and asks you to adjust them until they add up to exactly 100% before calculating trades.
This tool runs entirely in your browser. What you enter or upload stays on your device and is never sent to our servers.