Separate fixed and variable expenses
Fixed expenses repeat on a schedule: housing, phone, insurance, subscriptions, and loans. Food and transport often vary and are clearer in a separate budget.
Convert annual or quarterly bills to monthly equivalents before comparison.
- Monthly: enter as paid
- Quarterly: divide by 3
- Annual: divide by 12
Match income to take-home cash
Use monthly take-home income for practical cash-flow planning. Exclude irregular side income conservatively or test it as a separate average scenario.
For a household budget, align whose income and shared expenses are included.
Example: 1.5 million won fixed from 3 million
With 3 million won take-home and 1.5 million in fixed costs, the ratio is 50% and the annual fixed total is 18 million won.
The remaining 1.5 million still needs to cover variable spending, irregular costs, and savings.
- Fixed ratio = monthly fixed costs ÷ monthly income × 100
- Annual fixed cost = monthly fixed cost × 12
- Available amount = income - fixed cost
Find forgotten recurring charges
Review three months of transfers and card statements for unused apps, cloud storage, memberships, and installments.
There is no universal ideal ratio. This is a budgeting check, not personal financial advice.
Build a complete fixed-cost list from statements
Use three recent months of bank transfers, card recurring charges, and app-store subscriptions rather than memory. Include small cloud, media, membership, installment, rental, and education charges as well as housing, loans, and insurance. Mark charges that vary slightly but continue until cancellation as semi-fixed.
Convert quarterly and annual bills to a monthly equivalent while also recording the cash due in the payment month. Annual insurance of 1.2 million won equals 100,000 per month for comparison, but the full 1.2 million still needs to be available at renewal. Keep deposits and one-time appliances outside recurring fixed expenses.
- Review three months of recurring transactions
- Track both monthly equivalent and payment month
- Separate one-time purchases from recurring costs
Match the scope of income and expenses
For an individual budget, use that person's take-home income and actual personal obligations. For a household, combine the income and shared expenses of the same people. Comparing one person's income with all family housing costs, or household income with only selected expenses, produces a ratio that cannot be interpreted consistently.
For bonuses and freelance income, calculate a six- to twelve-month average and a separate conservative case. With 3.2 million won take-home and 1.45 million fixed, the ratio is about 45.3% and 1.75 million remains. That remainder must still fund food, transport, health, irregular bills, and saving, so read both the percentage and amount.
- Choose individual or household scope once
- Separate average and conservative variable-income cases
- Read the fixed ratio with the remaining cash
Prioritize fixed-cost reductions
Classify costs by amount, use frequency, necessity, and cancellation difficulty. Remove unused small subscriptions first; review contract, coverage, and early-repayment implications before changing phone, insurance, or loans. For housing and other slow-to-change costs, record the next renewal date and a target amount.
Set a monetary target such as 200,000 won per month and remove candidate items one at a time. Three 12,000-won subscriptions plus a 30,000-won membership save 66,000 monthly or 792,000 annually. Insurance cuts require a coverage-gap check, and loan changes should use an actual lender quote including fees.
- Classify by size, usage, necessity, and exit cost
- Calculate monthly and annual savings
- Check coverage and finance fees separately
Maintain a monthly review and FAQ
On the same day each month, record planned cost, actual charge, difference, and reason. Set reminders one month before renewal and check duplicated family subscriptions. A lower ratio caused only by a temporary income increase is different from a durable expense reduction.
There is no universal ideal fixed-cost ratio; housing, dependants, location, and income stability matter. Treat a high result as a prompt to review variable spending and emergency capacity, not an automatic verdict. Do not make tax, investment, debt, or insurance decisions from this estimate alone.
A lower displayed fixed cost does not always create more spending capacity. Annual billing, installments, and shifted due dates can move cash between months, so confirm savings across a full twelve-month cash schedule.
- Compare plan with actual charges monthly
- Check renewals, trials, and duplicate subscriptions
- Use contract terms or professional advice for high-impact decisions