Calculator Guide

Finance

Finance functions cover interest, growth, loans, annuities, returns, and common business calculations.

simple interest(10000, 5%, 2 years)
compound interest(1000, 12%, 24 months, 12)
emi(500000, 6.5%, 30 years)
cagr(1000, 2000, 10 years)

Argument conventions

Finance functions use parentheses and comma-separated arguments.

Argument	How to write it
Rate	`5%` or `5`; both mean five percent
Term / time	`2 years`, `18 months`, `30 years 12 months`, or bare years
Compounding frequency	A bare number of periods per year, such as `12` for monthly
Money	Currency symbols are ignored, so `$10000` and `10000` are equivalent

Rates are percentage values. Write 5% or 5 for five percent. Do not write 0.05 unless you mean 0.05%.

Interest and growth

Function	Description	Example
`simple interest(p, r, t)`	Interest only	`simple interest(10000, 5%, 2 years)`
`compound interest(p, r, t, n)`	Compound interest earned	`compound interest(1000, 10%, 2 years)`
`future value(p, r, t, n)`	Principal plus compound growth	`future value(1000, 10%, 2 years)`
`present value(fv, r, t, n)`	Present value of a future amount	`present value(1210, 10%, 2 years)`
`cagr(start, end, t)`	Compound annual growth rate	`cagr(1000, 2000, 10 years)`

The compounding frequency is optional for compound functions. If you omit it, Hissab compounds annually.

compound interest(1000, 10%, 2 years)
compound interest(1000, 12%, 24 months, 12)
future value(1000, 10%, 2 years)
present value(1210, 10%, 2 years)
cagr(50000, 75000, 5 years)

Loans and mortgage

emi, mortgage, and loan payment calculate the monthly payment for an amortizing loan.

emi(500000, 6.5%, 30 years)
mortgage(500000, 6.5%, 30 years)
loan interest(100000, 12%, 1 year)

Use loan interest when you need the total interest paid over the life of the loan.

Annuities

Annuity functions work with equal payments made each period.

future value annuity(1000, 10%, 3 years)
present value annuity(500, 8%, 10 years, 12)

Returns and business math

Function	Description	Example
`roi(initial, final)`	Return on investment	`roi(1000, 1500)`
`apy(rate, frequency)`	Effective annual yield	`apy(12%, 12)`
`profit margin(revenue, cost)`	Profit as a percent of revenue	`profit margin(200, 150)`
`markup(cost, price)`	Markup over cost	`markup(150, 200)`
`break even(fixed, price, variable)`	Units needed to break even	`break even(10000, 50, 30)`
`runway(cash, burn)`	Months of cash runway	`runway(100000, 8000)`
`doubling time(rate)`	Rule-of-72 estimate in years	`doubling time(8%)`

roi(1000, 1500)
apy(12%, 12)
profit margin(200, 150)
markup(150, 200)
break even(10000, 50, 30)
runway(2000000, 150000)
doubling time(8%)

Consumer

Everyday money math for tips, discounts, and tax.

Function	Description	Example
`tip(bill, rate)`	Tip amount	`tip(80, 18%)`
`tip total(bill, rate)`	Bill including the tip	`tip total(80, 18%)`
`discount(price, rate)`	Sale price after a discount (alias `sale price`)	`discount(200, 25%)`
`sales tax(price, rate)`	Tax on a price	`sales tax(100, 8%)`
`price with tax(price, rate)`	Price including tax	`price with tax(100, 8%)`

tip(80, 18%)
tip total(80, 18%)
discount(200, 25%)
sales tax(100, 8%)
price with tax(100, 8%)

Investment appraisal

Function	Description	Example
`npv(rate, cf0, cf1, ...)`	Net present value of a cashflow series; the first cashflow is at t = 0	`npv(10%, -1000, 500, 500, 500)`
`irr(cf0, cf1, ...)`	Internal rate of return, as a percent	`irr(-1000, 500, 500, 500)`
`depreciation(cost, salvage, life)`	Straight-line depreciation per year	`depreciation(10000, 1000, 5)`

irr needs at least one negative and one positive cashflow (a sign change). life may be a bare number of years or carry the years unit.

npv(10%, -1000, 500, 500, 500)
irr(-1000, 500, 500, 500)
depreciation(10000, 1000, 5)
depreciation(10000, 1000, 5 years)

Return values

Amount functions return money-like numbers: simple interest, compound interest, future value, present value, emi, loan interest, and the annuity functions.
Rate functions return percentage values: cagr, roi, apy, profit margin, and markup.
break even returns units. runway returns months. doubling time returns years.
Consumer and investment functions return money (tip, tip total, discount, sales tax, price with tax, npv, depreciation); irr returns a percentage.

To get principal plus simple interest, add the principal yourself.

10000 + simple interest(10000, 5%, 2 years)

Common mistakes

simple interest(10000, 0.05, 2 years) reads the rate as 0.05%, not 5%. Use simple interest(10000, 5%, 2 years).
rule of 72(8%) is invalid because function names cannot contain digits. Use doubling time(8%).
compound interest(1000, 10%, 5) uses five years and annual compounding. Add a frequency, such as compound interest(1000, 10%, 5 years, 12), for monthly compounding.