Money Market Growth Worked Examples: Tiered Rate Scenarios

July 20, 2026

Four worked examples: a balance sitting entirely within one rate tier, a balance spanning two tiers, contributions that cross a threshold mid-term, and a fee-adjusted comparison.

Example 1 — Balance Entirely Within the First Tier

$40,000 balance, tier structure: 3.09% up to $1,000,000, 3.64% above. Term: 1 year, no contributions.

Entire $40,000 falls within Tier 1 (under $1,000,000)
Effective APY = 3.09% (no blending needed)
Ending balance ≈ $40,000 × 1.0309 ≈ $41,236

Since the whole balance sits below the tier threshold, no blending occurs — the account simply earns Tier 1’s rate on the full amount.

Example 2 — Balance Spanning Two Tiers

$1,200,000 balance, same tier structure (3.09% / 3.64%), 1 year, no contributions.

Tier 1 portion: $1,000,000 × 3.09%
Tier 2 portion: $200,000 × 3.64%
Blended effective APY ≈ 3.18%
Ending balance ≈ $1,200,000 × 1.0318 ≈ $1,238,160

Only the $200,000 above the threshold earns the higher 3.64% rate — the blended rate lands closer to Tier 1’s rate than Tier 2’s, since most of the balance still sits in the lower tier.

Example 3 — Contributions Crossing the Tier Threshold Mid-Term

Starting balance $900,000, contributing $50,000/month, same tier structure, 3-year term.

Month 1-2: balance under $1,000,000 → entire balance earns 3.09%
Month 2 onward: balance crosses $1,000,000 → blended rate begins climbing toward 3.64%
By later months: most of the growing balance sits in Tier 2, pushing the blended rate closer to 3.64%

Because the money market calculator rechecks the applicable tier every month rather than locking in a single blended rate up front, this projection captures the gradually rising effective rate as contributions push the balance further into Tier 2 — a meaningfully different (and more accurate) result than assuming one static blended rate for the full 3-year term.

Example 4 — Fee-Adjusted Comparison

$8,000 balance, single flat 3.5% APY, 1 year, with a $10/month maintenance fee the calculator itself doesn’t model.

Calculator's raw projection: $8,000 × 1.035 ≈ $8,280
Annual fees: $10 × 12 = $120
Realistic ending balance: $8,280 − $120 ≈ $8,160

The $120 in annual fees reduces the effective real-world return by more than a third of a percentage point on this balance — see common money market calculation mistakes for why account fees need to be checked and subtracted manually, since the calculator’s compounding formula doesn’t know about them.

Running These Yourself

Every projection above matches what the money market calculator produces from the same principal, tier structure, contribution, and term inputs — enter your own account’s actual numbers to reproduce these results or model a scenario not covered here. For any term used in the tier structures above, see the money market account terms glossary.