Decision guide
How Much Cash to Keep in Checking
Last updated: October 2026
Checking accounts pay close to nothing. The FDIC national average for interest checking was 0.07% in September 2026. Every dollar that sits there past what you need for the month is a dollar not earning a savings rate.
This calculator sets a checking target of one month of outflows plus a cushion, shows how much to move to savings, and prices the idle cash in dollars per year after tax. It also compares the cost of your cushion with the cost of an overdraft fee, so you can size it on purpose.
Inputs
What leaves checking, what it holds, what savings pays.
Calculating the default example.
Checking is for the month ahead
Checking has one job: pay what is due before the next paycheck arrives. One month of outflows does that. The cushion covers the days when a bill clears before pay lands, or when spending runs higher than usual.
Anything above that target is savings sitting in the wrong account. The second result is what that costs you each year, after tax on the interest you would have earned.
Balance checks
The calculator assumes steady rates for a year, interest taxed at your rate, and savings that can move back to checking within a day or two.
What each checking balance costs
Each row shows the interest you give up by holding that balance in checking instead of savings, after tax. The second column shows how far each balance sits above or below your target.
| Checking Balance | Amount | Versus Target | Given Up Each Year | Given Up Over Five Years |
|---|
Example 1: $15,000 sitting in checking
Suppose $4,500 leaves your checking account in a typical month, and it holds $15,000 at 0.07%. A savings account pays 3.5%, and your interest is taxed at 22%.
The target is $5,500: one month of outflows plus a $1,000 cushion. That leaves $9,500 to move. At the higher rate it earns about $254.16 more a year after tax, or $1,343.55 over five years with compounding.
Leaving three months of bills in checking, $13,500, gives up $361.18 a year compared with keeping it all in savings. The $1,000 cushion costs $26.75 a year, less than one $35 overdraft fee. That is a cheap insurance policy.
Example 2: the savings account matters more than the amount
Now move the same $9,500, but into a savings account that pays the FDIC national average, 0.37% as of September 2026. The extra interest drops to $22.23 a year, and $111.92 over five years.
The gap between 0.37% and 3.5% is worth over ten times the gap between 0.07% and 0.37%. Before deciding how much to move, compare the rate on the account you would move it to. Search for a federally insured savings account that pays close to the rate on short Treasury bills.
Example 3: a cushion sized on purpose
A larger cushion protects against overdrafts, but it costs interest. At the rates in Example 1, each $1,000 of cushion gives up $26.75 a year. A $3,000 cushion gives up $80.26, a little more than two typical overdraft fees a year.
If you have never overdrawn and your income is steady, a smaller cushion with low-balance alerts is likely the cheaper choice. If your pay varies, or bills cluster early in the month, a larger cushion pays for itself after one avoided fee.
National rates and overdraft facts
The FDIC publishes national average deposit rates each month. As of September 21, 2026, the national rate was 0.37% for savings, 0.07% for interest checking, and 0.63% for money market accounts. These are averages across many banks, so individual accounts pay well above or below them.
A Consumer Financial Protection Bureau study described the typical overdraft fee as roughly $35. The CFPB lists ways to avoid debit card overdraft fees: decline debit card overdraft coverage or cancel it, link a savings account to cover shortfalls, sign up for low-balance alerts, and know when your automatic payments come out.
How the target and cost are calculated
The checking target is your monthly outflows plus the cushion. Money above the target moves to savings. The yearly cost of a balance is the balance times the gap between the savings APY and the checking APY, times one minus your tax rate. The five-year cost compounds each rate yearly after tax and takes the difference.
The comparison with overdraft fees divides the cushion's yearly cost by the fee. It is a rough guide to how many overdrafts the cushion would need to prevent each year to pay for itself. See the methodology limitations.
Mistakes with checking balances
- Treating checking as the emergency fund.
- Moving cash to a savings account that pays close to the national average.
- Sizing checking on take-home pay instead of on what actually leaves the account.
- Forgetting annual bills such as insurance that hit checking in one month.
- Moving so much that a large automatic payment overdraws the account.
Good fits
- Deciding how much to sweep into savings today.
- Pricing a larger or smaller cushion.
- Showing what a low savings rate costs.
- Setting a target for an automatic transfer.
Limits
- Business accounts with large swings in cash.
- Accounts with minimum balance fees. Add the fee threshold to the cushion.
- Choosing between savings, CDs, and Treasury bills. Use the after-tax cash comparison.
- Sizing an emergency fund. Use the emergency fund calculator.
Checking and savings questions
These answers cover how to size checking and what the calculator assumes.
How much money should I keep in checking?
Enough to cover one month of what leaves the account, plus a cushion for bills that land before your paycheck. Money above that earns more in a savings account and can move back in a day or two.
What counts as monthly outflows?
Everything that leaves checking in a typical month: rent or mortgage, bills, card payments, transfers, and spending on the debit card. Add up the last two or three statements and take the average.
How big should the cushion be?
Big enough to cover the gap between when bills clear and when pay arrives. If your income is steady and bills are predictable, a few hundred dollars is often enough. Irregular income calls for more.
Is my emergency fund part of this?
No. Keep the emergency fund in savings, separate from checking. This calculator only sizes the money you need for the month ahead.
How much does idle cash in checking cost?
The gap between the savings and checking rates, after tax, on every dollar above your target. In the main example, $9,500 of extra checking cash gives up $254.16 a year.
Does it matter which savings account I use?
More than how much you move. The FDIC national average savings rate was 0.37% in September 2026. At that rate, moving the same $9,500 earns only $22.23 more a year.
How do I avoid overdrafts with a smaller balance?
Link savings to checking for overdraft transfers, set low-balance alerts, and know the dates of your automatic payments. You can also decline debit card overdraft coverage so purchases are declined instead of charged a fee.
Is this financial advice?
No. It is an educational estimate, not financial or tax advice. Rates change often, so use the rates your bank quotes today.
Put the rest of your cash to work
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Educational estimate only. This calculator does not provide financial or tax advice. Rates change often. Use the rates your bank quotes today before moving money.