Self-Storage Unit vs Larger Apartment Cost Calculator

Urban living often means choosing between squeezing belongings into small quarters or renting additional space. Many renters automatically reach for self-storage when closets overflow, yet upgrading to a slightly larger apartment can sometimes be the cheaper (and simpler) option. This calculator helps you estimate that trade-off using a consistent yardstick: cost per square foot.

• What you’ll learn: the implied monthly “rent” of the storage space if it were part of your apartment, the total cost of each option over your chosen time period, and the monthly break-even point where storage and “more apartment” cost the same.
• What you’ll enter: your current apartment rent and size, the storage unit’s rent and size, and the number of months you want to compare.

How the calculator compares the two options

The calculator treats the storage unit’s square footage as “extra space you could have in a larger apartment” and values that extra space using what you already pay per square foot in your current place. That creates an apples-to-apples estimate:

1. Apartment implied cost for extra space: (your apartment $/sq ft) × (storage unit sq ft)
2. Storage cost: the storage unit monthly rent you enter
3. Totals: each monthly cost × number of months

Formulas used (with definitions)

1) Current apartment cost per square foot (per month)

Where:

• R = current apartment rent (per month)
• S = current apartment size (sq ft)
• C_sf = apartment cost per square foot per month

2) Implied extra apartment rent for the storage-sized space

Implied extra rent per month = Csf × U

• U = storage unit size (sq ft)

3) Total costs over N months

• Total storage cost = StorageRent × N
• Total implied apartment upgrade cost = (Csf × U) × N

4) Monthly break-even (storage rent that equals implied extra rent)

Break-even storage rent = Csf × U

If the storage unit’s actual rent is below this number, storage is cheaper (under this simplified model). If it’s above, paying for additional apartment space is cheaper.

Worked example (complete)

Scenario:

• Current apartment rent: $1,800/month
• Current apartment size: 600 sq ft
• Storage unit size: 50 sq ft
• Storage unit rent: $120/month
• Months to compare: 12

Step 1: Apartment cost per square foot

$1,800 ÷ 600 = $3.00 per sq ft per month

Step 2: Implied monthly cost of 50 extra sq ft in the apartment

$3.00 × 50 = $150/month

Step 3: Compare monthly costs

• Storage: $120/month
• Implied extra apartment space: $150/month

Under the calculator’s assumption (same $/sq ft), storage is cheaper by $30/month.

Step 4: Compare totals over 12 months

• Total storage cost: $120 × 12 = $1,440
• Total implied apartment upgrade cost: $150 × 12 = $1,800

Over one year, storage is cheaper by $360 in this example.

Interpreting your results

• If storage total is lower: renting storage is (likely) the cheaper way to get the extra space—assuming you can tolerate the inconvenience and any extra fees are small.
• If implied apartment extra-space total is lower: you’re paying a high effective price for storage relative to what you pay for your home space, so upgrading may be cost-effective (and you’ll avoid off-site access hassles).
• If they’re close: non-price factors often decide: convenience, security, access hours, parking/loading, and how long you truly need the space.

Quick comparison table (what the calculator includes)

Limitations and assumptions (important)

• Average $/sq ft vs marginal rent: The calculator assumes the next chunk of apartment space costs the same per square foot as your current apartment. In reality, the marginal jump from a studio to a 1BR (or 1BR to 2BR) may be higher or lower than your current average.
• Storage fees and promotions: Many facilities add admin fees, mandatory insurance, taxes, locks, or rates that increase after an introductory promo period. If those apply, your true storage cost will be higher than the entered rent.
• Move-in/move-out costs: Upgrading apartments can involve application fees, deposits, broker fees, moving costs, truck rentals, and time off work. Storage can also involve a van/truck, packing supplies, and repeated travel.
• Rent increases over time: The calculator assumes rents are constant across the comparison months. If you expect increases (or a promo ending), you may want to run multiple scenarios.
• Quality differences: A larger apartment might come with building amenities, better location, parking, or utilities that change the “value” beyond square footage alone.
• Non-financial factors: Convenience, security, climate control, pest risk, and access frequency can outweigh small dollar differences.

Rule-of-thumb decision tip

If you’re unsure how to interpret a close result, try changing the months. Storage often looks better for short timeframes (temporary transitions), while upgrading can look better if you need the space long-term and storage rates rise over time.