# Rent Split Calculator — Split Rent & Bills Fairly > Split rent and shared bills between housemates by equal share, room size or income. Handles move-in proration and always sums back to the exact total. - **Category:** Lifestyle & Everyday - **Calculator:** https://youcalc.com/en/lifestyle-everyday/rent-split-calculator/ - **Price:** Free · no sign-up ## About this calculator Sharing a flat means agreeing on a number, and "just divide it by three" stops being obviously fair the moment one room is twice the size of another, or one housemate earns half what the others do, or somebody moves in on the 16th. This calculator takes the total rent plus any shared bills and divides them by a rule your household picks — equally, by private room size, or by income — with day-based proration for a mid-month arrival. Every share is worked out in whole minor units of your currency, so the parts always add back up to the total instead of drifting a cent away from it. ## How to read your results The headline is what the household is actually being asked to pay between them, and the table underneath is the answer you will send round the group chat: days present, rent, bills and total due for each person. The "% of pot" column shows how the burden is distributed; the "cost ÷ income" column divides each person's full-month rent-plus-bills by their income and flags it against the affordability benchmark you selected. If someone moved in mid-month on the default proration setting, an "uncovered gap" figure appears — that is rent for the days the room stood empty, and it is shown rather than silently spread onto the other housemates. ## How it's calculated Each split method turns into a weight per person: equal is wᵢ = 1; income is wᵢ = incomeᵢ; room size with shared space per head is wᵢ = n·aᵢ + C (algebraically aᵢ + C/n, scaled by the headcount to stay in whole numbers), and room size with shared space excluded is simply wᵢ = aᵢ. Proration multiplies the weight by daysᵢ = D − moveInDayᵢ + 1. The money is then allocated by the largest-remainder method in integer minor units: W = Σwᵢ, each person gets qᵢ = ⌊T·wᵢ/W⌋, the exact remainders rᵢ = T·wᵢ − qᵢ·W are ranked, and the R = T − Σqᵢ leftover units go to the largest remainders, ties broken by row order. Because Σqᵢ is within n of T, R is always between 0 and n−1, so Σaᵢ = T exactly and nobody is more than one minor unit from their exact entitlement. Rent and every bill are allocated separately, so each line item reconciles on its own. Areas are converted using 1 ft² = 0.09290304 m² exactly, and the affordability flag uses the published threshold for the market you choose — 30% of income in the United States, 40% in the European Union — rather than treating either as a worldwide rule. ## Worked example - **Your inputs:** Rent 1,000 a month, three housemates with 18 m², 14 m² and 10 m² private rooms sharing a 40 m² kitchen, hallway and bathroom, split by room size with the shared space counted per head. - **Results:** The shares come out at 382.12, 333.33 and 284.55, which sum to exactly 1,000.00. Notice how much gentler this is than splitting on private area alone: that would charge 428.57 / 333.33 / 238.10, because it pretends the person in the 10 m² room uses the kitchen less than everyone else. The middle room lands on a third of the rent either way, which is the useful sanity check — 14 m² happens to be the household average. ## Frequently asked questions ### Should the kitchen and living room count in a room-size split? Yes, and the usual way is to charge for them per head. Hallways, kitchens, bathrooms and living rooms belong to nobody in particular and everybody has the same claim on them, so the fair treatment is to split the rent into a private-space portion (allocated by room size) and a shared-space portion (split equally). That is exactly what the default setting does. Excluding shared space entirely is simpler but harsher: it charges the person in the smallest room as if they also used the kitchen least, which is rarely true. A third option some tools offer — "in proportion to the whole flat's footprint" — is not actually a third option at all: because the shares have to add up to one, the shared area cancels out of every ratio and you get numbers identical to excluding it. ### Someone moved in on the 16th. Who covers the first half of the month? By default, nobody — and that is deliberate. Each person is charged their normal share multiplied by the days they were actually there, so a housemate arriving on the 16th of a 30-day month pays half. The rent for the empty half-month then shows up as an "uncovered gap", because it is usually the landlord's or the outgoing tenant's problem, not something the remaining housemates silently absorb. If your household has agreed to cover the full rent regardless, switch the proration setting to "cover the full rent anyway" and the whole amount is allocated between whoever was present. ### Why do the per-person shares sometimes differ by a single cent? Because most totals do not divide evenly. A thousand split three ways is 333.333… each, which cannot be paid in real money. Rounding each share on its own gives 333.33 three times and loses a cent; rounding up gives 333.34 three times and invents one. The largest-remainder method used here hands the leftover units to the people with the largest fractional entitlements, so one person pays 333.34 and the other two pay 333.33, and the total is exactly right. The same logic is why an income split of 1,000 between earners of 3,200, 2,400 and 1,800 comes out as 432.43 / 324.33 / 243.24 rather than the naive 432.43 / 324.32 / 243.24, which would quietly leave a cent unpaid. ### Is 30% of income really the limit for rent? It is the United States rule, not a global one. US federal housing policy fixes the tenant contribution at 30% of monthly adjusted income (24 CFR § 5.628) and the Census Bureau calls a household cost-burdened above 30% and severely cost-burdened above 50%. The European Union uses a different figure entirely: Eurostat's housing cost overburden rate kicks in above 40% of disposable income. Plenty of markets publish no official threshold at all, which is why this calculator asks you to pick a benchmark and shows no flag when you choose none — quoting an American number at a household in Karachi or Jakarta would be worse than saying nothing. ### Should the ratio use rent only, or rent plus bills? Rent plus the shared bills. The US Census measures housing burden on gross rent, which it defines as contract rent plus the utilities and fuels the tenant pays. A flat with cheap rent and brutal heating bills is not the bargain the rent alone suggests, and leaving utilities out systematically understates the burden in exactly the housing stock where it matters most. The calculator also uses the full-month figures for this ratio rather than a prorated first month, since a half-month bill would flatter the number without telling you anything about affordability. ### Does splitting by room size guarantee nobody feels cheated? No, and it is worth being honest about that. Proportional-to-area is a reasonable rule, not a provably fair one: it assumes every square metre is worth the same to everyone, which stops being true as soon as one room has the window, the ensuite, the morning sun or the noisy street outside. The rigorous version of this problem — assigning rooms and prices together so that nobody would rather have someone else's room at someone else's price — is the "rental harmony" result, and it needs each housemate to answer a series of questions about which room they would take at which price. That is a different kind of tool. This one gives you a defensible number and tells you what it is not. ## Related calculators - [Rent Affordability Calculator](https://youcalc.com/en/lifestyle-everyday/rent-affordability/) - [Rent vs. Buy Calculator](https://youcalc.com/en/lifestyle-everyday/rent-vs-buy/) - [Budget Planner](https://youcalc.com/en/finance-money/budget-planner/) - [Tip Calculator](https://youcalc.com/en/lifestyle-everyday/tip/) ## Sources - https://www.law.cornell.edu/cfr/text/24/5.628 — Legal Information Institute - https://www.census.gov/newsroom/press-releases/2024/renter-households-cost-burdened-race.html — United States Census Bureau - https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Housing_cost_overburden_rate — European Commission - https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication811e2008.pdf — National Institute of Standards and Technology - https://scholarship.claremont.edu/hmc_fac_pub/663/ — The Claremont Colleges --- Open full calculator: https://youcalc.com/en/lifestyle-everyday/rent-split-calculator/ · YouCalc — https://youcalc.com