Design the sheet around rate periods, not a memorized function
A compound-interest spreadsheet needs the starting amount, a clearly defined rate, the number of periods and any cash added at each period. The period for the rate must match the period for contributions and counting. Excel and Google Sheets provide an FV function, but a correctly typed function can still answer the wrong question if annual and monthly inputs are mixed.
This worksheet reproduces a constant nominal annual rate with selected compounding frequency, matching NumUtility's Compound Interest Calculator. It is not a forecast, a historical investment backtest or an account-specific interest calculation. Actual rate changes, irregular deposits, fees and tax treatment require a revised model rather than a claim that one formula already incorporates them.
Set up labeled cells with a single rate convention
Use B2 for initial principal, B3 for nominal annual rate entered as a percentage, B4 for periods per year, B5 for whole years, B6 for deposit per period and B7 for timing, with 0 meaning end and 1 meaning beginning. For a hypothetical example, enter 4,000; 4.8%; 12; 2; 100; and 0 in those respective cells.
Set B8 to =B3/B4 for the periodic rate, which is 0.4 percent per month, and B9 to =B4*B5 for 24 periods. A true 4.8% cell already stores 0.048 and must not be divided by 100 again. If the input is an effective annual yield rather than nominal rate, the monthly conversion needs a root, not this division; label that as a different sheet variant.
Verify the no-deposit formula before adding cash flows
With deposit set to zero, the direct formula is =B2*(1+B8)^B9. It compounds the starting principal for the number of matching periods. Setting the rate to zero should leave the initial principal unchanged. Setting the number of periods to zero should also return the initial amount, because no growth interval has occurred.
These boundary checks reveal an extra period, a rate entered as 4.8 rather than 4.8%, or an accidental simple-interest formula. Keep the direct formula as an independent check beside FV. If both cells refer to the same incorrect rate or period count, their agreement alone does not validate the interpretation, so retain the labeled inputs and a hand-checked first period too.
Use FV with cash-flow signs and timing made explicit
For the stated setup, =FV(B8,B9,-B6,-B2,B7) returns a positive ending asset balance. From the saver perspective, the opening principal and deposits are cash paid into the account, hence negative arguments in this convention. The positive result is the future value. Do not make every argument positive and then remove an unexplained minus sign only because the output looks inconvenient.
The example produces approximately $6,915.90 after 24 end-month deposits. Opening principal plus deposits is $4,000 + 24 × $100 = $6,400, so modeled interest is about $515.90. A large ending account value is not itself all interest. Keep a contribution total beside the future value so that funding and growth are reconciled rather than combined under an earnings label.
Reproduce the result with a month-by-month ledger
Place period zero's $4,000 opening balance in B15. For end-month contributions, the next balance formula is =B15*(1+$B$8)+$B$6. Copy it through exactly 24 growth-and-deposit rows. The first month ends at $4,116, and the twelfth ends at about $5,423.04. The twenty-fourth agrees with the unrounded FV calculation before display rounding.
For beginning-month deposits, the matching recurrence is =(B15+$B$6)*(1+$B$8), and the FV timing argument must be 1. Do not apply beginning timing to the ledger while leaving FV at 0. An off-by-one row or an extra deposit at period zero changes the cash provided and makes an apparently small mismatch a different financial scenario.
Keep periodic deposits fixed only when the funding plan is fixed
B6 means money per selected period, not automatically money per month under every frequency. Changing B4 from 12 to 365 while retaining a $100 deposit changes annual contributions from $1,200 to $36,500. The resulting balance difference is mostly a funding change, not an isolated gain from daily compounding. Read the contribution total before attributing a larger result to frequency.
For a compounding-frequency comparison of untouched money, set deposits to zero. For different contribution calendars, build an explicitly matched annual budget and appropriate timing rather than assuming the same cell value is comparable. The weekly-versus-monthly savings guide uses a separate equal-budget illustration; the current calculator does not accept a weekly frequency.
Choose rounding and copying rules deliberately
Display currency to cents without automatically rounding the balance after every row unless that is the model being reproduced. Repeated cent rounding can differ from a closed-form calculation that retains precision until the end. If you choose a rounded ledger, disclose it and compare with a rounded reference rather than demand exact equality to unrounded FV.
Use absolute references for shared input cells when copying formulas, and inspect the last row to confirm that its rate still points to B8. Blank inputs, text-formatted numbers and unsupported timing entries should be detected before interpreting outputs. Locale settings may change function names and argument separators; the examples use English names and comma-separated function arguments.
Cross-check the spreadsheet against the calculator's documented inputs
In the Compound Interest Calculator, enter $4,000 principal, nominal annual rate 4.8, two years, monthly compounding, $100 per period and end timing. Compare balance, total contributed and interest rather than only the largest number. The rate field expects 4.8 as a percentage number, while the worksheet's percentage cell stores 0.048. Both represent the same intended annual rate when used correctly.
This spreadsheet recipe is educational, not a recommendation to seek a particular return or deposit plan. The current calculator accepts whole-year horizons and nonnegative deposits; a sheet with another horizon or withdrawals is outside that exact interface comparison. Preserve those differences rather than describe a flexible spreadsheet function as proof of a feature the site does not implement.