Why 50/50 Feels Wrong
Splitting bills down the middle seems fair until you live with the results.
If one partner earns more than the other, a 50/50 split means the lower earner gives up a bigger chunk of their paycheck. Same dollars, different sacrifice.
Say you and your partner share $1,200 in rent. You earn $55,000 a year. Your partner earns $35,000. Split evenly, you each pay $600.
But that $600 is about 13% of your income—and 21% of theirs. One of you is carrying more weight.
Why 50/50 Works with Roommates (But Not Partners)
With a roommate, 50/50 makes sense. You're splitting the cost of shared space, not building a life together. If your roommate is stretched thin after rent, that's their problem to solve. You're not invested in their financial stress.
With a partner, it's different. Their stress is your stress. If they're scraping by while you've got money to spare, that tension lives in the house with you. You'll feel it even if nobody says anything.
Proportional splitting isn't about charity—it's about recognizing that your partner's financial breathing room directly affects your life together.
What Fair Actually Looks Like
Fair isn't about matching dollars. It's about matching effort.
When each partner contributes the same percentage of their income toward shared bills, the burden is equal. The higher earner pays more in dollars, but both feel it the same way on payday.
This is called proportional splitting. It's the foundation of how Cobalance works.
How It Works (No Algebra Required)
Take your total shared bills. Figure out what percentage that is of your combined income. Then each partner pays that percentage of their own income.
That's it. Both of you end up sacrificing the same slice of your paycheck.
A Real Example
Jim earns $2,200 every two weeks. Ashley earns $600 every week. Together that's about $88,400 a year. Their shared bills total $35,000 a year.
$35,000 out of $88,400 is roughly 40%. So both Jim and Ashley put 40% of their income toward bills.
For Jim, that's about $871 per paycheck. For Ashley, it's about $238 per paycheck.
Different dollars. Same sacrifice.
But Here's What Most Calculators Miss
Most "split bills by income" tools stop at the monthly number. They'll tell you Jim owes $1,888/month and Ashley owes $1,029/month.
That's not useful.
What you actually need to know: How much do I send from each paycheck so the bills account never goes negative?
That depends on when each person gets paid, when each bill hits, and whether the timing works—or whether you'll overdraft on the 28th waiting for the 1st.
This is what Cobalance solves. Not just the split. The orchestration.
When Proportional Splitting Doesn't Fit
Proportional splitting assumes both partners have income. But what if one partner is staying home with kids, job-hunting after a move, or back in school?
In those cases, a different model works better: all income goes to bills first, then each partner gets an equal personal allowance. Fair without requiring two incomes. We'll cover this in a future post.
The Bottom Line
Fair isn't 50/50. It's proportional.
When both partners pay the same percentage of their income, you eliminate the quiet resentment that builds when one person is stretched thinner than the other.
The math is simple. The effect on your relationship isn't.