TongTin Calculator (ROSCA)
Plan a Khmer TongTin savings circle: see who receives how much each round, what every member pays, and who ends up gaining or paying interest.
TongTin Settings
The discount each waiting member gets in the round. Set 0 for a no-interest TongTin, or edit each round in the schedule.
Round Schedule
| Round | Date | Receiver | Bid | Waiting Member Pays | Received Member Pays | Receiver Gets | Organizer: Cash Flow |
|---|---|---|---|---|---|---|---|
| 1 | — | Organizer | — | $100.00 | $100.00 | $900.00 | +$900.00 |
| 2 | — | Member 2 | $5.00 | $95.00 | $100.00 | $860.00 | -$100.00 |
| 3 | — | Member 3 | $5.00 | $95.00 | $100.00 | $865.00 | -$100.00 |
| 4 | — | Member 4 | $5.00 | $95.00 | $100.00 | $870.00 | -$100.00 |
| 5 | — | Member 5 | $5.00 | $95.00 | $100.00 | $875.00 | -$100.00 |
| 6 | — | Member 6 | $5.00 | $95.00 | $100.00 | $880.00 | -$100.00 |
| 7 | — | Member 7 | $5.00 | $95.00 | $100.00 | $885.00 | -$100.00 |
| 8 | — | Member 8 | $5.00 | $95.00 | $100.00 | $890.00 | -$100.00 |
| 9 | — | Member 9 | $5.00 | $95.00 | $100.00 | $895.00 | -$100.00 |
| 10 | — | Member 10 | — | $100.00 | $100.00 | $900.00 | -$100.00 |
Member Summary
| Member | Round | Total Paid | Received | Net Gain / Cost | Return |
|---|---|---|---|---|---|
| Organizer | 1 | $900.00 | $900.00 | $0.00 | 0.00% |
| Member 2 | 2 | $900.00 | $860.00 | -$40.00 | -4.44% |
| Member 3 | 3 | $895.00 | $865.00 | -$30.00 | -3.35% |
| Member 4 | 4 | $890.00 | $870.00 | -$20.00 | -2.25% |
| Member 5 | 5 | $885.00 | $875.00 | -$10.00 | -1.13% |
| Member 6 | 6 | $880.00 | $880.00 | $0.00 | 0.00% |
| Member 7 | 7 | $875.00 | $885.00 | +$10.00 | 1.14% |
| Member 8 | 8 | $870.00 | $890.00 | +$20.00 | 2.30% |
| Member 9 | 9 | $865.00 | $895.00 | +$30.00 | 3.47% |
| Member 10 | 10 | $860.00 | $900.00 | +$40.00 | 4.65% |
How TongTin Works
1. What is a TongTin?
TongTin (តុងទីន) is a rotating savings and credit association, or ROSCA. A group contributes a fixed amount each round, and one member receives the collected money. It repeats until every member has received once.
2. How are the payments calculated?
Members still waiting pay the contribution minus the round's bid. Members who already received pay the full contribution. The receiver gets the sum of what everyone else pays: (rounds already received × contribution) + (waiting members × (contribution − bid)).
3. Who gains and who pays?
Receiving early works like a loan, so early members usually pay more than they receive. Waiting works like saving, so later members earn the bids. Net amounts across all members always add up to zero. Rules differ between groups, so check that these match yours.
4. What are the risks?
A TongTin depends on trust. It is usually not insured or regulated, so a member or organizer who stops paying can cause real losses. This calculator assumes everyone pays in full and on time.
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