Enter a negative number to indicate a withdrawal.
name · target % · current value · share price
Minimize transaction costs when rebalancing your fund portfolio
The Bogleheads philosophy rests on three pillars: low-cost index funds, broad diversification, and staying the course. One of its most practical techniques is contribution-based rebalancing: instead of selling overweight funds and paying taxes and fees, you simply direct new money toward the funds that have fallen below their target.
This calculator finds the mathematically optimal allocation of your contribution so your portfolio ends up as close as possible to your target, with zero sells.
Try the calculator →Different assets grow at different rates. Over months and years, a 55/15/10/10/10 portfolio quietly becomes 63/11/8/9/9 and your risk profile changes with it.
Selling triggers taxes and transaction costs. Instead, put new contributions to work in the underweight funds. Same result, lower cost, and you stay fully invested.
This tool uses exact arithmetic to find the allocation that brings your portfolio closest to target. No rounding heuristics, no guesswork. Just the right number of shares to buy.
Type the amount you're adding to your portfolio this period. Use a negative number for withdrawals.
List each fund with its target allocation (%), current total value, and share price. One fund per line.
Hit Run calculation. The table shows exactly how many shares of each fund to buy to restore your target allocation.