★ COMPARISONS · HOME VS BUYING · POTATO SOUP
On the defaults — 20 days at $4.00 an potato soup at home versus $12.00 bought — home costs $80.00 against $240.00 buying, so home saves $160.00 a month and $1,920.00 a year. This is the POTATO SOUP version — the daily-habit comparison for potato soupes.
Put your days per month, home cost per bowl of potato soup and buying cost per bowl of potato soup in: 20 days at $4.00 home vs $12.00 bought — home $80.00 vs buying $240.00, home saves $160.00 a month, $1,920.00 over 12 months.
It means making at home costs $80.00 for 20 days while buying costs $240.00 for the same 20 days — a gap of $8.00 a bowl, $160.00 a month, $1,920.00 over a year. The home total is 33.33% of the buying total, so every bought bowl of potato soup you replace with a homemade bowl keeps $8.00 in your pocket. The break-even buying price is $4.00 a day: a café bowl of potato soup at any price above $4.00 loses to homemade, and only a bowl of potato soup at or below $4.00 ties or beats it.
| Output | Formula | What it means |
|---|---|---|
| Home total per month | days × home cost per bowl | $80.00 — 20 × $4.00. |
| Buying total per month | days × buying cost per bowl | $240.00 — 20 × $12.00. |
| Monthly saving | buying total − home total | $160.00 — $240.00 − $80.00. |
| Yearly saving | monthly saving × 12 | $1,920.00 — $160.00 × 12. |
| Break-even buying price | home cost per bowl | $4.00 a day — the bought price at which home stops winning. |
| Home cost behind a target saving | buying cost − target saving ÷ days | $4.00 — $12.00 − $160.00 ÷ 20. |
| Buying cost behind a target saving | home cost + target saving ÷ days | $12.00 — $4.00 + $160.00 ÷ 20. |
| Days behind a target saving | target saving ÷ (buying cost − home cost) | 20 — $160.00 ÷ $8.00. |
First, the home cost must be the full per-bowl cost: potatoes, stock and cream, plus a share of the butter and cream. Pricing only the potatoes makes homemade look cheaper than it is. Second, the buying price must be what you actually pay per bowl, including delivery or service charges on that potato soup — a menu price without the extras understates the buying total. Third, the day count must match reality: 20 days means an potato soup on 20 days of the month, whether homemade or bought, and counting days you skip inflates both totals and the saving.
Days 20, home $4.00, buying $12.00. Home total: 20 × $4.00 = $80.00. Buying total: 20 × $12.00 = $240.00. Monthly saving: $240.00 − $80.00 = $160.00. Yearly saving: $160.00 × 12 = $1,920.00. Drop to 10 days and the saving falls to $80.00 a month; drop to 15 days and it is $120.00 a month; rise to 25 days and it climbs to $200.00 a month; rise to 30 days and it reaches $240.00 a month. The saving scales exactly with the days, because the $8.00 per-bowl gap never changes.
A home cost of $4.50 with the same days and buying cost gives home $90.00 vs buying $240.00, a saving of $150.00 a month. A buying cost of $11.50 with the same days and home cost gives home $80.00 vs buying $230.00, a saving of $150.00 a month. Fifteen days with the same home and buying costs gives home $60.00 vs buying $180.00, a saving of $120.00 a month. Twenty-five days with the same home and buying costs gives home $100.00 vs buying $300.00, a saving of $200.00 a month. Each branch changes exactly one input, so the difference from $160.00 isolates that input.
The home cost behind $160.00 a month saved is $4.00: at $3.50 the figures are home $70.00 vs buying $240.00, a saving of $170.00 a month, and at $4.50 they are home $90.00 vs buying $240.00, a saving of $150.00 a month — a $0.50 step moves the saving by $10.00, because it applies to all 20 days. The buying cost behind $160.00 a month saved is $12.00: at $11.50 the saving is $150.00 a month, and at $12.50 it is $170.00 a month — a $1.00 step moves the saving by $20.00, because it applies to all 20 days. The days behind $160.00 a month saved are 20: at 15 days the saving is $120.00 a month, and at 25 days it is $200.00 a month — five days either way moves the saving by $40.00.
The defaults assume one bowl of potato soup on each of 20 days, a steady $4.00 home cost and a steady $12.00 bought price, all year. Real potato soup habits cluster around busy workday mornings, so the honest use is to enter your average month, or to run the calculator once per stretch of the year and add the stretches. Zero days is the honest edge: home $0.00 vs buying $0.00, exactly even. Negative inputs are rejected, and a home cost above the buying price flips the verdict honestly: at a buying price of $3.00 against $4.00 home, home costs $20.00 more a month over 20 days, and buying wins.
A daily potato soup buyer weighing a homemade habit: the $160.00 monthly gap is the prize, and the $1,920.00 yearly gap is the reason to keep potatoes and stock on hand. A parent planning family breakfasts: the home line prices a bowl of potato soup made at home against the bowl of potato soup bought at the café on the way to school. A home cook testing prices: the break-even of $4.00 a day is the floor a home cook must beat, and the buying line is the price a customer compares against. A household cutting food spending without giving up potato soupes: the days line shows exactly how much each skipped potato soup day is worth.
The arithmetic is exact for the inputs entered; the judgement is in the inputs. A home cost that omits the cheese or the eggs, a buying price that omits delivery, or a day count that includes skipped days will each move the answer by exactly the amount of the error, every month. The model does not include your time, the cost of a stockpot bought once, or the value of a café bowl of potato soup you enjoy more — price those separately, and re-check the comparison when ingredient or café prices change. This page is a calculation tool, not financial advice.
Home potato soup $4.00 vs $12.00, over 20 days: home $80.00 vs $240.00, saves $160.00 a month, $1,920.00 a year. Break-even $4.00 a day. Free calculator. Source: Bright Side Kit, https://brightoolbox.com/making-potato-soup-at-home-vs-buying-potato-soup/, accessed 31 October 2026 (2026-10-31).
Everything in one bowl: potatoes, stock and cream, priced per bowl of potato soup. A bag of potatoes that makes 10 bowls divides its potato cost by 10; leaving out the cream understates the home line.
Use your average price: the month total uses one home cost, so enter the average per bowl across the month. A week of cheap eggs and a week of dear eggs average out, and the saving follows the average.
Not in this comparison, which prices ingredients against the café price. If your time matters to you, value it separately: at $20.00 an hour, an hour of preparation a month adds $20.00 to the home line.
Because home wins whenever the bought price exceeds the home cost per bowl: at a bought price of $4.00 the two totals tie, and above it every bowl saves the difference. That is why the break-even buying price is $4.00 a day.
Yes — whenever the home cost rises above the bought price. At a buying price of $3.00 against $4.00 home, home costs $20.00 more a month over 20 days, and buying wins by exactly that amount.
Multiply the monthly saving by 12: $160.00 × 12 = $1,920.00. That is the year total if the habit holds steady; for a habit that runs only part of the year, multiply by the months it actually runs.