omacus
// use cases

Sheets for the math in your week

A notepad calculator shines when a calculation has a story: who paid, which hours, what's left. Here are seven real sheets, each answer calculated by Omacus itself.

Each sheet below is plain text you could type into Omacus as-is. Lines starting with # are headers, // starts a note, words before a colon are labels, and the answers on the right appear as you type. total adds up the block above it, and prev is the line before.

Splitting a group trip

Four friends, five nights in Kyoto. Flights are in dollars and everything else in yen, as it's booked; total adds it all up in one currency, and each person's share is converted for the friends paying in euros and pounds. The last lines check the time back home.

Kyoto in autumn
  1. # Kyoto in autumn
  2. // 4 friends, 5 nights
  4. Flights: 4 * $1,180$4,720
  5. Ryokan: 5 nights * ¥68,000340,000 JPY
  6. Rail passes 4 * ¥50,000200,000 JPY
  7. Dinners ¥14,000 * 4 * 5280,000 JPY
  8. total$9,907.02
  9. each = prev / 4$2,476.75
  11. each in EUR2,208.40 EUR
  12. each in GBP1,867.60 GBP
  14. Lands 4:10pm JST in San Francisco12:10 AM PDT
  15. Call home 8pm JST in New York7:00 AM EDT

Related: currency conversion, time zones.

A freelance invoice with tax

Set the hourly rate once, list the work, and let sum and a named tax line do the rest. Change the rate and every line below updates.

Invoice — October
  1. # Invoice — October
  2. rate = $150/hour$150 / hour
  4. Design review 6 hours * rate$900
  5. Build 32 hours * rate$4,800
  6. Client calls 4.5 hours * rate$675
  7. subtotal = sum$6,375
  8. tax = 8.875% of subtotal$565.78
  9. subtotal + tax$6,940.78
  10. prev in EUR6,188.75 EUR

Related: percentages.

A monthly budget

Income at the top, spending in a block, and a quick check of how much of the income it takes.

Monthly budget
  1. # Monthly budget
  2. income = $6,200$6,200
  4. Rent: $1,850$1,850
  5. Groceries $420 + $95$515
  6. Internet $60$60
  7. Gym $45$45
  8. total$2,470
  9. prev as % of income39.84%
  10. savings = 20% of income$1,240

Scaling a recipe

Double a recipe by changing one number, and convert the oven temperature while you're at it.

Banana bread, doubled
  1. # Banana bread, doubled
  2. scale = 22
  4. Flour: 250 g * scale500 g
  5. Sugar: 150 g * scale300 g
  6. Butter: 115 g * scale230 g
  7. Milk: 0.5 cups * scale in ml236.59 ml
  8. Bananas: 3 * scale6
  10. Oven: 350 fahrenheit in celsius176.67 °C
  11. Bake: 55 min + 10 min65 mins

Related: unit conversion.

Picking a meeting time across time zones

Try a time, read down the column, adjust. Omacus flags when a time falls on the next day.

Weekly sync, Tuesday
  1. # Weekly sync, Tuesday
  2. // proposed: 9am in San Francisco
  3. 9am PST in New York12:00 PM EDT
  4. 9am PST in London5:00 PM BST
  5. 9am PST in Berlin6:00 PM CEST
  6. 9am PST in Tokyo1:00 AM JST (next day)
  8. // Tokyo would be up at 1am. Try the afternoon:
  9. 4pm PST in Tokyo8:00 AM JST (next day)
  10. 4pm PST in Berlin1:00 AM CEST (next day)
  11. 4pm PST in London12:00 AM BST (next day)

Related: time zones.

Planning a road trip

Distance and fuel economy give the fuel needed; the price per liter turns it into money; dividing by your speed gives the driving time.

Road trip to the coast
  1. # Road trip to the coast
  2. distance = 1,200 km1,200 km
  3. mileage = 15 km/liter15 km / liter
  4. fuel = distance / mileage80 liters
  6. Fuel: fuel * $1.45/liter$116
  7. Tolls $38$38
  8. Snacks $25 * 3$75
  9. total$229
  10. each = prev / 4$57.25
  12. Driving: distance / 90 km/h13.33 h
  13. distance in miles745.65 miles

Related: unit conversion.

Comparing a purchase

A discount, sales tax, monthly payments, and the same model from a store abroad.

New laptop
  1. # New laptop
  2. price = $1,299$1,299
  3. deal = 15% off price$1,104.15
  4. with_tax = deal + 8.875%$1,202.14
  5. monthly = with_tax / 12$100.18
  7. // same model, from the UK store
  8. uk = £1,049 in USD$1,391.15
  9. uk - with_tax$189.01

Related: percentages, currency conversion.

Questions

What is a notepad calculator?

A calculator you use like a notepad: you write calculations in plain words, one per line, alongside notes, and each line shows its answer. Unlike a regular calculator, nothing disappears, and changing one line updates everything that depends on it.

Can I keep several sheets?

Yes. Omacus has a sidebar of sheets, one per trip, budget or project, each saved automatically as a plain text file.

Can I use these sheets myself?

Yes. Copy any sheet above into Omacus and the answers appear as it's pasted. Exchange rates and time zones will reflect the day you paste it.

Time zones6pm PST in Tokyo, with daylight saving and next-day answers handled. Currency$30 in EUR, mixed currencies, symbols or codes, offline. Percentages15% off, + 8% tax, X is what % of Y, and every other phrasing. Unit conversionkm in miles, cups in ml, °F in °C, and math with units.

Try it on your own numbers.

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