Uncertain use over three months: calculate low and high quantities
By Erik Nilsen · Kroni2 min read
A known price does not establish a certain period cost when refill quantities vary. For optional consumption, write the quantities assumed by the plan. A low estimate should not become a guarantee that the budget will last.
Keep price fixed and vary quantity
In a hypothetical example, one pack of personal stickers costs 9 units. Your child plans between two and five packs monthly over three months. The arbitrary price and usage are invented, and each pack is purchased only when actually chosen.
Low use means 3 × 2 = 6 packs costing 6 × 9 = 54 units. High use means 3 × 5 = 15 packs costing 15 × 9 = 135. The cost range comes from quantity rather than a changing item price.
A period budget of 90 covers 90 / 9 = 10 packs. It cannot cover three months using five each month. An actual split of two, five and three packs gives 2 + 5 + 3 = 10 and fits exactly.
Check the combined quantity during the period
A practical snag is saying “I can use five this month” without noticing that another five next month would consume the entire ten-pack limit. After two and five, seven have been used and three remain within the plan.
Write quantity and payment for each month. Update both what has been used and what remains possible. Your child can choose fewer packs; the estimate describes options rather than a duty to buy.
Do not add 54 and 135 as two expenses. They represent possible scenarios for the same period. When purchases occur, record the actual quantity and payment in the history.
Ask your family: “Which combined quantity does our budget cover, and how much have we already chosen?”
Carry the calculation into your family agreement
Kroni can keep track of your child's virtual balance. The app does not transfer money, so any actual purchase is paid for outside it. Agree on what you will record, then check the amount with your child afterwards. Do not deduct a possible cost as though the purchase had already happened. Read about allowance in Kroni.
