How to Split Bills with Roommates: 7 Fair Methods That Actually Work

The Polish Utility Structure Explained

• Czynsz (administrative fee / maintenance fee): This is NOT rent. It is a monthly fee paid to the building management (spoldzielnia or wspolnota) for maintenance, common area cleaning, sometimes heating and water. It is usually fixed and ranges from 400-900 PLN per month. It is always shared.
• Electricity (prąd): Billed separately, usually every 2 months by the energy provider. Ranges from 150-400 PLN per billing period for a shared apartment. Always shared.
• Gas (gaz): If the apartment has gas heating or a gas stove. Billed separately. Ranges from 50-300 PLN per billing period depending on season. Always shared.
• Water: Sometimes included in czynsz, sometimes billed separately. If separate: 50-150 PLN per person per month. Always shared.
• Internet: A separate contract, typically 60-120 PLN per month. Always shared.
• TV/Streaming subscriptions: Optional. Shared by agreement.
• Groceries: The most contentious category. Shared or separate by agreement.
• Cleaning supplies: Small but frequently forgotten. Shared.

Typical Monthly Shared Expenses in Polish Apartments

Method 1: The Equal Split

How it works: Total shared expenses divided equally among all flatmates, regardless of room size, income, or usage.

Example: Three flatmates, 1,500 PLN total shared expenses. Each pays 500 PLN.

Pros: Dead simple. No calculations, no tracking, no arguments about who used more hot water. Everyone knows exactly what they owe every month.

Cons: Feels unfair when rooms are significantly different sizes, when one person works from home and uses more electricity, or when income differences are large.

Best for: Flatmates with similar-sized rooms, similar lifestyles, and similar incomes. The default choice when nobody has a strong reason to do it differently.

Method 2: Proportional to Room Size

How it works: Measure each bedroom's square meters. Calculate each person's share as a percentage of total private space. Apply that percentage to shared expenses.

Example: Room A is 15m2, Room B is 12m2, Room C is 10m2. Total: 37m2. Room A pays 40.5%, Room B pays 32.4%, Room C pays 27%. On 1,500 PLN shared expenses: A pays 608 PLN, B pays 486 PLN, C pays 405 PLN.

Pros: Objectively fair. The person with the biggest room pays more, which makes intuitive sense since they are occupying more of the shared property.

Cons: Requires measuring rooms. Can feel overly clinical. Does not account for room quality differences (window facing, noise exposure, proximity to bathroom).

Best for: Apartments with noticeably different room sizes. Particularly useful when one room is significantly larger or has special features like a balcony or en-suite bathroom.

Method 3: Income-Based Splitting

How it works: Each person contributes proportional to their income. The higher earner pays a larger share of shared expenses.

Example: Flatmate A earns 8,000 PLN/month, Flatmate B earns 5,000 PLN/month. Total income: 13,000 PLN. A pays 61.5% of shared expenses, B pays 38.5%.

Pros: Most equitable in terms of financial burden. Neither person sacrifices a disproportionate percentage of their income. Creates goodwill and reduces financial stress for the lower earner.

Cons: Requires sharing income information, which many people find uncomfortable. Can breed resentment from the higher earner who feels penalized for earning more. Income can fluctuate (freelancers, commissions), making calculations inconsistent.

Best for: Close friends or couples with significant income disparity who value equity over equality. Not recommended for flatmates who are strangers or casual acquaintances.

Method 4: Usage-Based Splitting

How it works: Track actual usage and bill each person for what they use. Fixed costs (internet, czynsz) split equally. Variable costs (electricity, gas, water) split by usage.

Example: The flatmate who works from home and runs the heater all day pays a larger electricity share. The one who takes 30-minute showers pays more for water.

Pros: Maximally fair in theory. Nobody subsidizes anyone else's consumption habits.

Cons: Extremely difficult to implement without sub-meters. Creates a nickel-and-diming atmosphere that poisons the living dynamic. Do you really want to track who left the light on?

Best for: Almost nobody. The administrative burden and social cost almost always outweigh the fairness benefit. Only consider this if there is a massive and obvious usage disparity (one person runs a home office with servers; the other is out 14 hours a day).

Method 5: Rotating Payments

How it works: Each person takes turns paying the full shared expenses for a month. Flatmate A pays everything in January, B pays in February, C pays in March, then back to A.

Example: Three flatmates with approximately 1,500 PLN monthly shared expenses. Each pays 1,500 PLN every third month instead of 500 PLN every month.

Pros: Simple to track. Only one person handles payments each month, reducing administrative overhead.

Cons: Only works when expenses are roughly consistent month to month. The person who pays during the winter heating month gets a bad deal. Requires enough cash flow to cover the full amount when it is your turn.

Best for: Small apartments with stable costs. Works well when expenses are consistent and all flatmates have stable, sufficient income.

Method 6: The Shared Fund (Kitty)

How it works: Each person contributes an equal (or agreed) amount to a shared bank account or cash fund at the beginning of each month. All shared expenses are paid from this fund.

Example: Each of three flatmates transfers 600 PLN to a shared account on the 1st. Bills are paid from that account. Any surplus rolls over. Any deficit is topped up equally.

Pros: Bills are always paid on time (one account, automatic payments). No one needs to chase anyone for money. Transparent: everyone can see the account balance.

Cons: Requires opening a shared bank account (doable in Poland with most banks). Risk if one person manages the account and trust breaks down. Requires agreement on what qualifies as a 'shared expense.'

Best for: Organized flatmates who want a clean, automated system. Particularly good for longer-term flat shares where consistency matters.

Method 7: App-Based Splitting

How it works: Use a bill-splitting app to track every shared expense in real time. Each person logs what they pay for, the app calculates running balances, and you settle up periodically.

Example: Flatmate A pays the internet bill (100 PLN), logs it in Splitwise, and the app shows B and C each owe A 33 PLN. When B buys cleaning supplies (60 PLN), A and C each owe B 20 PLN. The app nets it all out.

Pros: Precise, transparent, and eliminates mental math. Historical record of all expenses. Supports complex splitting rules (unequal splits, exclusions).

Cons: Only works if everyone actually uses the app. Can create a transactional atmosphere if overused for tiny expenses. Requires periodic 'settling up' sessions.

Best for: Most modern flat shares, especially those with variable expenses. The most popular method among international flatmates in Poland.

Our recommendation: Splitwise for expense tracking + Revolut or Blik for instant payments. This combination covers logging, calculating, and settling in a seamless workflow.

When to Have It

Ideally, before signing the lease. At the latest, during the first week of living together. Frame it as a practical setup task, not a confrontation: 'Let us sort out the bills system so we never have to think about it again.'

What to Cover

• Which expenses are shared: Rent, czynsz, utilities, internet, cleaning supplies. What about groceries? What about streaming subscriptions?
• How expenses will be split: Equal? Proportional? App-based? Agree on one method and stick to it.
• Payment deadline: When is rent due? When does each person need to transfer their share? Agree on a specific date (e.g., 'Transfers by the 3rd of each month').
• What happens when someone is late: A grace period? A late fee? Covering for each other temporarily? Having this agreed in advance removes the emotional charge from the situation if it happens.
• Groceries policy: Shared shopping or separate? If shared, what is the monthly grocery budget per person? If separate, how do you handle shared basics (salt, oil, toilet paper)?
• Tracking tool: Agree on Splitwise, a shared spreadsheet, or another method. Everyone installs it on day one.
• Review schedule: Monthly check-in to make sure the system is working and no one has unresolved concerns.

A Template You Can Use

Here is a simple shared expenses agreement template. Copy it, fill it in with your flatmates, and keep a copy each.

Shared Expenses Agreement
Date: ___
Flatmates: [names]
Address: ___

1. Shared expenses include: [list them]
2. Splitting method: [equal / proportional / app-based]
3. Payment deadline: [date] each month
4. Tracking tool: [Splitwise / spreadsheet / etc.]
5. Late payment policy: [grace period / penalty]
6. Groceries: [shared / separate / shared basics only]
7. Monthly budget for shared items: [amount] PLN
8. Review: First [day] of each month

Signed: ___ ___ ___