Portfolio Allocation Calculator
Use this portfolio allocation calculator to see how much to buy or sell in stocks, bonds and cash to rebalance back to your target mix.
What it does
The Portfolio Allocation Calculator compares what you hold today in stocks, bonds and cash with the mix you want, then tells you exactly how much to buy or sell in each bucket to get back on target.
Data sources & parameters
This calculator uses standard financial formulas and runs entirely in your browser. It needs no external rate data — your result is computed only from the values you enter above.
We always strive to use the latest data for every variable so our results and reports are as accurate as possible. Even so, errors are possible — you should not rely on this tool or its report alone, and we accept no liability for any decision made based on it.
The formula
target_amount = total × target_pct ÷ 100; trade = target_amount − current_value
How it works
It adds your three balances into a total, applies your target percentages to that total to find the ideal amount for each asset class, and subtracts what you already hold. A positive trade means buy, a negative trade means sell or withdraw.
Where it is used
- Rebalancing a portfolio back to its target weights
- Deploying a lump sum of cash across asset classes
- Checking how far your current mix has drifted from plan
Worked example
A portfolio holds $6,000.00 in stocks, $3,000.00 in bonds and $1,000.00 in cash, and wants a 70/20/10 split. The tool says to trade … in stocks, … in bonds and … in cash to reach the target.
What the portfolio allocation calculator does
The portfolio allocation calculator compares the mix of assets you hold today with the mix you want and tells you the trades needed to close the gap. You enter the current value of your stocks, bonds and cash and your target weights for stocks and bonds, and the tool works out how much to buy or sell in each bucket. Rebalancing then becomes a mechanical task instead of a judgement made in a rising or falling market.
Why asset allocation matters
The split of your money between stocks, bonds and cash is one of the biggest drivers of the risk and return you experience. Stocks offer higher long-run growth but swing sharply in value. Bonds are steadier and cushion the ride. Cash is stable and liquid but loses ground to inflation over time.
Once you have chosen a target mix that matches your goals and tolerance for risk, keeping the portfolio close to it preserves that risk profile. Left alone, a portfolio drifts.
How portfolios drift
In a strong year for shares, your stock holdings can grow far faster than your bonds, lifting equities from a planned 70 percent to 78 percent or more of the total. That feels fine while the market climbs, but the portfolio now carries more risk than you intended, which hurts most in a downturn.
A sharp fall in shares does the reverse, leaving you underweight equities and overweight cash and bonds, so you may be too cautious to benefit fully from a recovery. The calculator measures that drift in money terms and tells you what to trade to undo it.
How the calculation works
The tool adds your three balances to find the total value of the portfolio, then applies your target percentages to that total. The stock and bond targets come from your inputs, and the cash target is whatever is left over, so the three always sum to 100 percent.
It then compares each target amount with what you hold. A positive difference means buy or add money to that bucket; a negative one means sell or withdraw; zero means that asset class is on target. The maths is pure arithmetic, so the tool works in any currency and any market.
How to use the calculator
- Enter the current value of your stock holdings.
- Enter the current value of your bond holdings.
- Enter the current value of your cash.
- Enter your target percentages for stocks and bonds; cash fills the remainder.
The tool shows the trade needed in each bucket, your total portfolio value, and the implied cash target.
Applying the results
If a suggested trade is tiny relative to the portfolio, it may not be worth the transaction cost or the tax on any gain, so many investors set a tolerance band and rebalance only when drift exceeds it. If you are adding new money anyway, you can often rebalance by directing fresh contributions into the underweight buckets, without selling anything.
Selling an appreciated holding in a taxable account can trigger a tax bill, so where possible rebalance inside tax-sheltered accounts, or use new contributions and withdrawals to steer the mix. The calculator shows the end state; you choose the cheapest way to reach it.
Common mistakes
- Letting a hot asset class run because it feels good, which leaves the portfolio far riskier than planned. Rebalancing trims what has run and buys what has lagged.
- Rebalancing too often. Reacting to every small wobble adds costs and taxes for little benefit; a schedule or a threshold avoids overtrading.
- Ignoring taxes and costs. A trade that looks free on screen can carry real friction, so favour tax-sheltered accounts and new cash flows.
Checking your allocation on a regular schedule and making the small trades that bring it back keeps risk in line with your plan over decades.
This article is general information only and is not financial advice.
About This Portfolio Allocation Calculator
Use this portfolio allocation calculator to get an instant estimate based on the figures you enter. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.
Frequently asked questions
How does the portfolio allocation calculator work?
What is portfolio rebalancing?
How is the target cash allocation calculated?
What does a negative trade mean?
How often should I rebalance?
Is my data kept private?
About the author
