How SplitRent Calculates
Fair Rent

Full transparency: All formulas, factors and algorithms explained in detail.

Contents

The Zero-Sum Principle

Core guarantee: The total rent always stays exactly the same. All adjustments (quality, extras, income) sum to zero.

Σ Adjustments = 0 → Total rent unchanged

If one room pays more due to better quality, others pay correspondingly less. No one can be disadvantaged without someone else benefiting.

01 – Calculation Methods

SplitRent offers 5 calculation methods with increasing complexity. Choose the method that fits your shared apartment.

1

Size Only

The simplest method: rent is split purely by room size.

// Formula:
RoomRent = TotalRent × (RoomSize / TotalArea)
2

With Quality

Size plus 8 quality factors (light, noise, etc.).

RoomRent = BaseRent + QualityAdjustment
3

With Extras

Size + quality + room extras (balcony, private bathroom, etc.).

RoomRent = BaseRent + Quality + Extras
4

With Income

Everything above + income weighting (default: 30%).

RoomRent = CriteriaRent × (1 - Weight) + IncomeRent × Weight
5

Income Only

Purely income-based, room size is ignored.

RoomRent = TotalRent × (Income / TotalIncome)

02 – Quality Factors

Each room is rated on a scale of 0-100 (50 = neutral). The weight of each factor is customizable.

Factor Default Weight Max Adjustment Description
☀️ Daylight 100% ±5% Natural light in the room
🔇 Noise 100% ±5% Noise level (low = better)
🔒 Privacy 80% ±4% Room seclusion level
🏞️ View 60% ±3% View quality
💨 Ventilation 60% ±3% Air circulation
📍 Proximity 40% ±2% Distance to common areas
📐 Layout 80% ±4% Room shape & usability
🏢 Floor 40% ±2% Floor level of the room

Quality Adjustment Calculation

// Step 1: Deviation from neutral value

deviation = (value - 50) / 50 // Results in -1 to +1

// Step 2: Weighted adjustment

adjustment = deviation × weight × maxAdjustment × baseRent

// Step 3: Zero-sum distribution

finalAdjustment = rawValue - average // Sum = 0

03 – Extras & Amenities

Rooms with special features receive surcharges. All percentages are customizable.

🚿 Private Bathroom +12%
🚽 Private Toilet +6%
🌅 Balcony +8%
☂️ Terrace +10%
👔 Walk-In Closet +5%
🗄️ Built-In Closet +3%
📦 Storage Room +4%
🌿 Garden Access +7%
🔲 Corner Room +4%
⬆️ High Ceilings +3%

Extras Adjustment Calculation

// Example: Room with balcony and private bathroom

extrasPercent = 8% + 12% = 20%

rawValue = baseRent × 0.20

adjustment = rawValue - average // Zero-Sum

04 – Window Direction

Window orientation affects daylight and thus the living value.

⬆️
North
-5%
↗️
Northeast
-2%
➡️
East
0%
↘️
Southeast
+3%
⬇️
South
+5%
↙️
Southwest
+3%
⬅️
West
0%
↖️
Northwest
-2%
No Window
-8%

South-facing windows are most valuable (lots of sun), while north-facing windows provide less light. Rooms without windows receive the largest deduction.

05 – Income Weighting

Optionally, residents' income can be factored into the calculation. Default: 30% weight.

Blending Formula

FinalRent = CriteriaRent × (1 - w) + IncomeRent × w

At w = 30%: The final rent consists of 70% criteria-based calculation and 30% income-based.

0%

Income completely ignored

30%

Default: Moderate consideration

100%

Purely income-based

06 – Fairness Score

The Fairness Score (0-100) evaluates how equitable the rent distribution is.

Factor 1: Price/m² Variance (50%)

How much does the price per square meter differ between rooms?

20% variance = loss of 50 points

Factor 2: Rent/Income Ratio (30%)

How different is the rent-to-income ratio?

Only for income-based methods

Factor 3: Extreme Outliers (20%)

Are there rooms deviating more than 50% from average?

Additional penalty for extreme differences
90-100
Excellent
75-89
Good
60-74
Fair
40-59
Questionable
0-39
Unfair

Example Calculation

3-Room Apartment, Total Rent: €1,500

Room Size Base Quality Extras Final
Room A 15m² €450 +€27 +€54 €531
Room B 18m² €540 -€15 €0 €525
Room C 17m² €510 -€12 -€54 €444
Total 50m² €1,500 €0 €0 €1,500

Room A has better quality and a private bathroom (+12%), so pays more. Room C compensates through fewer extras and lower quality.

Calculate Fair Rent Now

Download SplitRent for free and calculate the perfect split for your shared apartment.

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