Savings & CD Calculator: APY Growth

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$

Starting balance

$

Added every month (flexible mode only)

%

Annual percentage yield — interest as actually earned, compounding included

How long the money grows

≈60 Months ⋅ 5 Years\approx \text{60 Months · 5 Years}

Your projection

$19,319.07

Total contributed
$17,000.00
Interest earned
$2,319.07
Monthly rate
0.327374%

Yearly breakdown

Yearly breakdown
YearBalanceContributedInterest
1$7,643.69$7,400.00$243.69
2$10,393.12$9,800.00$593.12
3$13,252.54$12,200.00$1,052.54
4$16,226.33$14,600.00$1,626.33
5$19,319.07$17,000.00$2,319.07

Savings & CD Calculator — APY Growth with Contributions

Estimate what 4% APY earns on $5,000 plus $200 a month. Enter the APY your bank quotes; the monthly rate is derived from it. Add contributions to see the projected balance split into contributions and interest. Switch to CD mode for a fixed term with no contributions and preset 3/6/12/60-month options.

Compare flexible savings against locked CDs, test what an extra $50 a month does over five years, and see the early-withdrawal estimate before you commit. Every calculation runs locally in your browser with no sign-up, and any scenario can be shared with a link.

The APY mechanics

m=(1+APY)1/12−1m = (1 + \text{APY})^{1/12} - 1
balance=P(1+m)n+C⋅(1+m)n−1m\text{balance} = P(1+m)^{n} + C \cdot \frac{(1+m)^{n} - 1}{m}

APY already includes compounding, so the monthly rate is derived from it rather than calculated by division. The balance is the closed-form monthly-compounded future value of the deposit plus the annuity value of the contributions.

P=initial depositP = \text{initial deposit} · C=monthly contributionC = \text{monthly contribution} · n=number of monthsn = \text{number of months}.

How it works

  1. Enter the APY — the yield as actually earned, compounding included.
  2. Add an initial deposit plus monthly contributions (flexible mode).
  3. Or flip to CD mode: contributions lock to 0, pick a preset term.

CD presets and the early-exit estimate

CD terms of 3, 6, 12 or 60 months are one tap away. Breaking early typically costs about 3 months of interest on the deposit — 10000 at 5% APY over 12 months grows to 10500.00, and an early exit costs ≈122.72\approx 122.72.

What v1 leaves out

APY growth plus CD lock plus penalty estimate only — no tax treatment, no inflation, no tiered rates in v1. Follow-ups add real-dollar and ladder views.

Frequently asked questions

APY vs APR — what's the difference?

APR is the quoted rate before compounding; APY is what you actually earn with compounding included. This tool takes APY directly, so you do not need to convert it.

When does a CD beat flexible savings?

When its APY is high enough to offset the lock-in. Compare both modes above on identical inputs to see the difference in balances.

How is the early-withdrawal penalty estimated?

As 3 months of interest on the initial deposit at the derived monthly rate. Real banks vary — treat it as an order-of-magnitude warning, not a quote.

When do contributions credit?

At the end of each month (ordinary annuity). Beginning-of-month contributions would earn slightly more; this tool uses the end-of-month convention.

How accurate is this calculator?

Exact to the cent against closed-form references: direct evaluation, no iterated rounding drift. Real accounts may compound daily rather than monthly — close, not identical.