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Split Mathematics & Net Settlement Algorithm

How Kestro computes fair domestic splits without complex accounting or tedious manual spreadsheet recalculations.

Section 1

The Income-Proportional Split Formula

When multiple earners share living expenses, a 50/50 split unfairly drains the lower earner. Kestro calculates each earner's contribution ratio based on declared monthly net income:

// For any earner i among n earning members:
Ratio(i) = Income(i) / TotalHouseholdIncome
OwedAmount(i) = TotalExpenseAmount × Ratio(i)

Worked Example:

  • • Rohan: Takes home ₹80,000/mo (64% of ₹1,25,000 total pool).
  • • Priya: Takes home ₹45,000/mo (36% of ₹1,25,000 total pool).
  • • Expense: D-Mart monthly grocery bill = ₹10,000.
  • • Rohan's Share: ₹10,000 × 0.64 = ₹6,400.
  • • Priya's Share: ₹10,000 × 0.36 = ₹3,600.
Section 2

The Settle-Up Debt Minimization Engine

In a joint family with 4 earners, pairwise debts quickly turn into a tangle: Brother A owes Brother B, who owes Sister C, who owes Brother A. Instead of 6 separate bank transfers, Kestro simplifies this into a minimal net balance:

Algorithm Steps:
  1. Calculate Net Balance: For each member u: Net(u) = Total Paid by u - Total Owed by u.
  2. Partition Groups: Divide members into Creditors (Net > 0) and Debtors (Net < 0).
  3. Greedy Match: Match largest debtor with largest creditor, reducing the total transaction count to at most N-1 transfers.

Try this formula right now

Test your own numbers in our interactive browser split calculator with live visual bars.

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