joellewis/savings-goals

Savings Goals

Core Concepts

Required Monthly Savings

To accumulate a future value FV in n periods at rate r per period:

PMT = FV × r / [(1+r)^n - 1]

This is the sinking fund formula (future value of annuity solved for PMT).

Inflation-Adjusted Targets

Always compute goals in future (nominal) dollars:

FV_nominal = FV_today × (1 + inflation)^years

Then solve for the required savings using the nominal return, or use the real return with today's dollars.

Education Funding

• 529 plans: tax-free growth for qualified education expenses, state tax deductions in many states
• Current costs (2025-26, total cost of attendance, College Board Trends in College Pricing): ~$30K/year (public four-year in-state) to ~$65K/year (private nonprofit), growing ~5%/year
• Front-loading: maximize early contributions for compound growth
• Superfunding: 5-year gift tax averaging (contribute 5× annual exclusion at once)
• Financial aid impact: parent-owned 529 assets are assessed at a maximum of 5.64% in the federal Student Aid Index (SAI) formula — FAFSA has used the SAI in place of the Expected Family Contribution (EFC) since the 2024-25 award year

Retirement Accumulation

• Target nest egg: annual spending need / safe withdrawal rate
  • Example: $80K/year spending / 0.04 = $2,000,000
• Safe withdrawal rate: traditionally 4% (Bengen rule), adjusted for fees, taxes, longevity
• Required savings rate: depends on starting age, current savings, expected returns
• Employer match: always capture full match — it's an immediate 50-100% return
• Catch-up contributions: additional 401(k)/IRA contributions allowed after age 50

Down Payment Saving

• Typical target: 20% of home price (avoids PMI)
• Timeline: typically 2-7 years → conservative allocation (HYSA, short-term bonds)
• Include closing costs (2-5% of purchase price) in savings target

Goal Priority Framework

Recommended priority order:

1. Emergency fund (3-6 months expenses)
2. Employer 401(k) match (free money)
3. High-interest debt payoff (>6-8% rate)
4. HSA (triple tax advantage if eligible)
5. Max retirement accounts (401k, IRA, Roth)
6. Education funding (529)
7. Other goals (home, vacation, etc.)

Multiple Goal Balancing

• Allocate savings across goals based on priority, timeline, and flexibility
• Non-negotiable goals (retirement) take precedence over flexible goals
• Shorter timelines need more conservative investment allocation
• Use goal-based investing: separate sub-portfolios per goal with appropriate risk

Savings Rate Benchmarks

• Minimum: 15% of gross income for retirement (including employer match)
• Aggressive: 25-50%+ for early retirement / FIRE
• Savings rate = total savings / gross income

Key Formulas

| Formula | Expression | Use Case | |---------|-----------|----------| | Required savings (PMT) | PMT = FV × r / [(1+r)^n - 1] | Monthly savings for a goal | | Future value with savings | FV = PV(1+r)^n + PMT×[(1+r)^n - 1]/r | Project goal balance | | Inflation adjustment | FV_real = FV_today × (1+π)^t | Convert today's dollars to future | | Retirement target | Nest egg = annual spend / SWR | Size the retirement goal | | Years to goal | n = ln(FV×r/PMT + 1) / ln(1+r) | How long until goal is funded | | Savings rate | SR = total savings / gross income | Track savings discipline |

Worked Examples

Example 1: College Savings (529)

Given: Need $200,000 in 18 years, expect 7% annual return, starting from $0 Calculate: Required monthly savings Solution:

• Monthly rate: r = 0.07/12 = 0.005833
• Months: n = 18 × 12 = 216
• PMT = $200,000 × 0.005833 / [(1.005833)^216 - 1]
• PMT = $1,166.67 / [3.5125 - 1]
• PMT = $1,166.67 / 2.5125 = $464.34/month

Example 2: Retirement Accumulation

Given: Age 30, $50,000 currently saved, wants $2,000,000 by age 65, expects 8% annual return Calculate: Required monthly savings Solution:

• Monthly rate: r = 0.08/12 = 0.006667; months: n = 35 × 12 = 420
• FV of current savings (monthly compounding): $50,000 × (1.006667)^420 = $50,000 × 16.2925 = $814,627
• Remaining needed: $2,000,000 - $814,627 = $1,185,373
• PMT = $1,185,373 × 0.006667 / [(1.006667)^420 - 1]
• PMT = $7,902.49 / [16.2925 - 1]
• PMT = $7,902.49 / 15.2925 = $517/month
• With employer match of $200/mo: personal contribution = $317/month

Common Pitfalls

• Not inflation-adjusting future goals (college in 18 years costs much more than today)
• Neglecting employer match — it's the highest guaranteed return available
• Too conservative allocation for long-horizon goals (20+ years can tolerate equity risk)
• Saving for college before adequately funding retirement (retirement has no financial aid)
• Not revisiting savings rate as income grows (lifestyle creep absorbs raises)
• Using average returns without considering sequence risk near goal date

Cross-References

• time-value-of-money (core plugin, Layer 0): FV/PV calculations, annuity formulas
• emergency-fund (wealth-management plugin, Layer 6): must be funded before other goals
• debt-management (wealth-management plugin, Layer 6): high-interest debt payoff competes with savings
• tax-efficiency (wealth-management plugin, Layer 5): 529 tax benefits, Roth vs traditional, HSA
• investment-policy (wealth-management plugin, Layer 5): goal-based allocation aligns with IPS constraints
• asset-allocation (wealth-management plugin, Layer 4): glide paths for target-date retirement savings
• finance-psychology (wealth-management plugin, Layer 7): mental accounting, present bias, commitment devices
• financial-planning-workflow (advisory-practice plugin, Layer 10): savings goals are key inputs to the comprehensive financial planning process

Running the script

Run the reference implementation directly:

uv run scripts/savings_goals.py      # PEP 723 header resolves dependencies automatically
python3 scripts/savings_goals.py     # standard library only — no installs needed

A bare run prints a demo covering required monthly savings, retirement accumulation, time-to-goal, inflation adjustment, shortfall analysis, education funding, savings rate, and real returns. Use --verify to recompute the demo figures and assert they match this skill's worked examples (prints PASS/FAIL, exits nonzero on mismatch), and --help to list the available classes and functions. The file is primarily meant to be imported as a module (from savings_goals import SavingsGoals) rather than run standalone.