Help Grandma Out

The cookie formula

2 min read

The exact sum behind your cookies, and how to do it yourself.

The short version

Here is the whole sum in one line, dear: cookies = (what one plain hour is worth) x (Grandma's approval multiplier) x (your approved hours). One plain hour has a fixed cookie value. Grandma's multiplier goes up when you take on tougher challenges. Multiply those two by your approved hours, and you get your cookies.

What goes in

Here is each input that counts toward your total, dear:

  • Approved hours: the hours a reviewer approves, NOT the hours Hackatime tracked. A reviewer may reduce them if they look inflated, see payouts.
  • Demand tiers: the tier of each demand you kept (mild, medium, spicy).
  • Grandma loved it: a bonus when your project is exceptionally neat and well made.
  • Huge project: a bonus for building past Grandma's hours threshold (see the numbers table below).
  • Blue Ribbon: a bonus for exceptional work that earns a spot on the wall.
  • Held a Blue Ribbon before: the same bonus as the Blue Ribbon, on every later project once you have earned one. It is never counted twice, so a ribbon project made by a ribbon holder gets it once.

The exact formula

Here is the exact formula with all the current numbers Grandma uses, dear.

The numbers

Item Symbol Value
Cookies for one plain hour one plain hour 32.5
Multiplier cap cap 1.85
Curve constant k -0.8
Largest x xmax 1.3
Mild demand tier tier[1] 0.1
Medium demand tier tier[2] 0.2
Spicy demand tier tier[3] 0.3
Grandma loved it quality 0.2
Huge project bonus huge 0.1
Huge project hours threshold huge_hours 20
Blue Ribbon bonus ribbon 0.1

The three steps

  1. Step 1: Find x

    x equals the sum of the demand tiers you kept plus the bonuses that apply, but never more than the largest x (xmax).

    x = min(xmax, sum of kept demand tiers + quality + huge + ribbon)

    Filled in with Grandma's numbers:

    x = min(1.3, kept demands + bonuses)

    Where mild is 0.1, medium is 0.2, and spicy is 0.3. Bonuses are: Grandma loved it (0.2), huge project at 20 hours or more (0.1), Blue Ribbon (0.1). The Blue Ribbon bonus also counts on every project after your first ribbon, once, never twice.

  2. Step 2: Calculate the multiplier

    Grandma uses an exponential curve so the multiplier climbs faster as you stack harder challenges:

    multiplier = 1 + (cap - 1) * (1 - e^(-k * x)) / (1 - e^(-k * xmax))

    Filled in with Grandma's numbers:

    multiplier = 1 + (1.85 - 1) * (1 - e^(-(-0.8) * x)) / (1 - e^(-(-0.8) * 1.3))

  3. Step 3: Calculate cookies

    Multiply cookies for one plain hour by the multiplier and your approved hours:

    cookies = cookies for a plain hour * multiplier * approved hours

    Filled in with Grandma's numbers:

    cookies = 32.5 * multiplier * approved hours

Worked example: one mild demand, 12 hours

  1. Step 1 (find x): One mild demand gives tier value 0.1. With 12 hours (under 20 hours), no extra bonuses apply.
    x = min(1.3, 0.1) = 0.1
  2. Step 2 (calculate multiplier): Substitute x into Grandma's curve formula:
    multiplier = 1 + (1.85 - 1) * (1 - e^(-(-0.8) * 0.1)) / (1 - e^(-(-0.8) * 1.3))
    multiplier = 1 + 0.85 * (1 - e^(0.08)) / (1 - e^(1.04))
    multiplier = 1 + 0.85 * (1 - 1.0833) / (1 - 2.8292)
    multiplier = 1 + 0.85 * (-0.0833) / (-1.8292)
    multiplier = 1 + 0.85 * 0.0455 = 1.0387
  3. Step 3 (calculate cookies): Multiply cookies for one plain hour by the multiplier and your approved hours:
    cookies = 32.5 * 1.0387 * 12 = 405.09
    Rounded half up gives 405 cookies.

Reference cases

What was kept Hours Extras Cookies
One mild demand 12 None 405
One medium demand 12 Grandma loved it 458
One mild demand 60 Huge project 2107
Two medium demands 20 Huge project 799
Three spicy demands 20 Grandma loved it, Blue Ribbon, Huge project 1203
Three spicy demands 60 Grandma loved it, Blue Ribbon, Huge project 3608

Do it yourself, step by step

You can work out your cookies with three simple steps:

  1. Find x: Add up the tier value of each demand you kept, plus any bonuses that apply (Grandma loved it, huge project, or the Blue Ribbon, which also applies if you held one before, counted once). If the sum goes above the largest x in the table, use the largest x instead.
  2. Calculate the multiplier: Put your x into Grandma's curve formula. A standard calculator with an exponent key (e to the power) is enough to do this yourself.
  3. Calculate your cookies: Multiply what one plain hour is worth by your multiplier and your approved hours.

Take a look at the worked example in the formula box above to follow every step with real numbers.

Rounding

Grandma never gives you half a cookie, dear. The final result rounds half up to a whole cookie (0.5 rounds up), exactly like the calculator does.

Check yourself

The reference table in the formula box above lists six examples you can reproduce on your own calculator.

Try it

Move the sliders and test different combinations yourself:

Grandma scowling with her arms crossed in a big X

Pick a demand, dear. I'm waiting.0cookies

12 hours of building

Note

Any number you compute before review is an estimate. The reviewer's approved hours and Grandma's verdict decide the real one, and cookies are only handed over when you visit Grandma after the review.