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what is the mathematical formula that you would use to describe the financial activity on a bank statement?

The standard mathematical formula that describes the financial activity on a bank statement is:

Ending Balance=Previous Balance+Deposits−Withdrawals\text{Ending Balance}=\text{Previous Balance}+\text{Deposits}-\text{Withdrawals}Ending Balance=Previous Balance+Deposits−Withdrawals

Core idea in plain language

Think of your bank balance as a running total:

  • You start with a previous balance.
  • Every deposit (money coming in) is added.
  • Every withdrawal (money going out) is subtracted.

So over any period (say, for one month on a statement), the formula says:

Ending Balance=Starting Balance+Total Deposits−Total Withdrawals\text{Ending Balance}=\text{Starting Balance}+\text{Total Deposits}-\text{Total Withdrawals}Ending Balance=Starting Balance+Total Deposits−Total Withdrawals

A mini example:

  • Previous balance: 500
  • Total deposits: 300
  • Total withdrawals: 200

Then:

Ending Balance=500+300−200=600\text{Ending Balance}=500+300-200=600Ending Balance=500+300−200=600

Adding a bit more realism (fees, etc.)

Real bank statements often show fees or other charges. A slightly richer version of the formula is:

Ending Balance=Previous Balance+Deposits−Withdrawals−Fees\text{Ending Balance}=\text{Previous Balance}+\text{Deposits}-\text{Withdrawals}-\text{Fees}Ending Balance=Previous Balance+Deposits−Withdrawals−Fees

You can think of fees as a special type of withdrawal that you don’t directly initiate, but the bank does.

How this matches what you see on a statement

On a typical statement, each line is a transaction that either:

  • Increases the balance (deposit, interest, refund), or
  • Decreases the balance (ATM withdrawal, card purchase, fee, transfer out).

Mathematically, if you label each transaction amount as TiT_iTi​, where deposits are positive and withdrawals/fees are negative, then over the statement period:

Ending Balance=Previous Balance+∑iTi\text{Ending Balance}=\text{Previous Balance}+\sum_i T_iEnding Balance=Previous Balance+i∑​Ti​

This is just the same idea as the earlier formula, but written in a compact way that works for many transactions instead of just the totals.

SEO-style meta description

A simple formula to describe the financial activity on a bank statement is: Ending Balance = Previous Balance + Deposits − Withdrawals (and optionally − Fees), capturing how money in and out changes your account over time.