Financial Calculator

This page contains forms for computing the financial formulas described in the book:
YOU CAN DO THE MATH
Overcome Your Math Phobia and Make Better Financial Decisions

by Ron Lipsman
Published by Praeger Publishers

Each form gives the actual formula that is used. You only need to enter your data; the form will perform the appropriate computation for you and return the result of evaluating the formula using your data.
Click here if you need a rudimentary arithmetic calculator.
Return to Financial Forms Page

Chapter 1. Saving for a College Education

Lump Sum Account--Final Value
Simple Annual Interest
V = D(1+r)n
D is the amount deposited, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Daily Compounded Interest
V = D(1 + r/365)365n
D is the amount deposited, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Lump Sum Account--Target Value
Simple Annual Interest
D = V/(1+r)n
V is the final target value of the account, r is the interest rate,
n is the number of years, and D is the initial amount you must deposit.
Let V = Let r = Let n =   

Daily Compounded Interest
D = V/(1 + r/365)365n
V is the final target value of the account, r is the interest rate,
n is the number of years, and D is the initial amount you must deposit.
Let V = Let r = Let n =   

Chapter 2. Investing for a College Education

Regular Deposit Account--Final Value

Annual Deposit, Simple Annual Interest
V = D(1 + r)[(1 + r)n - 1] / r
D is the amount deposited annually, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Annual Deposit, Daily Compounded Interest
V = D(1 + r/365)365[(1 + r/365)365n - 1]/[(1 + r/365)365 - 1]
D is the amount deposited annually, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Monthly Deposit, Daily Compounded Interest
V = D(1 + r/360)30[(1 + r/360)360n - 1]/[(1 + r/360)30 - 1]
D is the amount deposited monthly, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Biweekly Deposit, Daily Compounded Interest
V = D(1 + r/364)14[(1 + r/364)364n - 1]/[(1 + r/364)14 - 1]
D is the amount deposited biweekly, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Weekly Deposit, Daily Compounded Interest
V = D(1 + r/364)7[(1 + r/364)364n - 1]/[(1 + r/364)7 - 1]
D is the amount deposited weekly, r is the interest rate,
n is the number of years, and V is the final amount.
Let D = Let r = Let n =   

Regular Deposit Account--Target Value

Annual Deposit, Simple Annual Interest
D = V/[(1 + r)[(1 + r)n - 1] / r]
V is the final target value of the account, r is the interest rate,
n is the number of years, and D is the amount deposited annually that is required.
Let V = Let r = Let n =   

Annual Deposit, Daily Compounded Interest
D = V/[(1 + r/365)365[(1 + r/365)365n - 1]/[(1 + r/365)365 - 1]]
V is the final target value of the account, r is the interest rate,
n is the number of years, and D is the required amount deposited annually.
Let V = Let r = Let n =   

Chapter 3. Taking into Consideration Taxes and Inflation

Inflating Prices
P = P0(1 + r)n
P0 is the price of an item initially, r is the annual inflation rate,
n is the number of years, and P is the final price.
Let P0 = Let r = Let n =   

After-Tax rate of Return
ra = r(1 - b/100)
r is the stated rate of return, b is the marginal income tax bracket,
and ra is the actual after-tax rate of return.
Let r = Let b =   

Effect of Taxes on a Simple Annual Interest Account
V = D(1+rb)n
D is the amount deposited, r is the interest rate,
n is the number of years, b is the marginal tax rate,
rb = r(1-b/100) is the effective yield, and V is the final amount.
Let D = Let r = Let b = Let n =   

Chapter 4. Tax-Deferred Accounts Can Help

Taxable versus Tax-Deferred; Simplest Model
V = D(1 + r)[(1 + r)n - 1] / r, in the tax-deferred account
V = D(1 + rb)[(1 + rb)n - 1] / rb, in the taxable account, rb=r(1-b/100)
D is the amount deposited annually, r is the interest rate,
n is the number of years, b is the marginal income tax bracket, and V is the final amount.
Let D = Let r = Let n = Let b =   

Taxable versus Tax-Deferred; Complex Model
V = (1-b/100)D(1 + r)[(1 + r)n - 1] / r, in the tax-deferred account
V = (1-b/100)D(1 + rb)[(1 + rb)n - 1] / rb, in the taxable account, rb=r(1-b/100)
D is the amount available (before taxes) annually, r is the interest rate,
n is the number of years, b is the marginal income tax bracket, and V is the final amount.
Let D = Let r = Let n = Let b =   

Chapter 5. Your First Salary: What is Your Job Worth

Freedom Quotient
FQ = AT/G is your after-tax income, G is your gross salary,
FQ is your freedom quotient.
Let AT = Let G =   

Chapter 6. Buying a House or Car: Mortgages and Loans

Loan Payments
P = B(r/12) / [ 1 - 1/(1+r/12)n ]
B is the amount borrowed, r is the interest rate,
n is the number of months, and P is the monthly payment.
Let B = Let r = Let n =   

Loan Amount
B = P/[(r/12) / [ 1 - 1/(1+r/12)n ]]
P is the monthly payment, r is the interest rate,
n is the number of months, and B is the amount borrowed.
Let P = Let r = Let n =   

Magic Number
MN = (r/12) / [ 1 - 1/(1+r/12)n ]
r is the interest rate, n is the number of months,
and MN is the magic number.
Let r = Let n =   

Total Payments
TP = nP = nB(r/12) / [ 1 - 1/(1+r/12)n ]
B is the amount borrowed, r is the interest rate,
n is the number of months, and TP is the total payment.
Let B = Let r = Let n =   

Total Interest
TI = TP - B
where the formula for TP is given in the form immediately above.
B is the amount borrowed, r is the interest rate,
n is the number of months, and TI is the total interest paid on the loan.
Let B = Let r = Let n =   

Chapter 7. Buying or Leasing Your Car

Lease Payments
P = (C - R)/n + (C + R)M
C is the cap cost, R is the residual value,
n is the number of months, M is the money factor,
and P is the monthly payment.
Let C = Let R = Let n = Let M =   

Chapter 10. Cut up those #$%^& Credit Cards

Credit Card Interest
I = Br/12
B is the outstanding balance, r is the annual interest rate charged by your credit card company,
and I is the interest charge for that month.
Let B = Let r =   

Chapter 12. The Stock Market and Other Investments

Escalating Investment Model
V = D(1 + r) [(1 + r)n - (1 + s)n] / (r - s)
D is the initial amount invested, r is the interest ate,
s is the rate at which the amount invested is escalated each year, n is the number of years,
and V is the final value.
Let D = Let r = Let s = Let n =   

Magic Number for an Escalating Investment Program
MN = (1 + r) [(1 + r)n - (1 + s)n] / (r - s)
r is the interest rate, s is the rate at which the amount invested is escalated each year,
n is the number of years, and MN is the magic number.
Let r = Let s = Let n =   

Chapter 13. Retirement

Retirement Account Depletion--Discounting Inflation
How Long Will Your Money Last
n = ln[S/(S - rE)]/ln(1+r)
S is the annual shortfall, E is your nest egg,
r is the interest rate, and n is the number of years till depletion of the account.
Let S = Let E = Let r =   

How Much You Can Spend
S = (1 + r)nE/[(1 + r)n - 1)/r]
E is your nest egg, r is the interest rate,
n is the number of years the nest egg must last, and S is the amount you can afford to spend annually.
Let E = Let r = Let n =   

Retirement Account Depletion--Accounting for Inflation
How Long Will Your Money Last
n = ln[S/(S - (r - s)E)]/ln[(1+r)/(1+s)]
S is the annual shortfall, E is your nest egg,
r is the interest rate, s is the inflation rate,
and n is the number of years till depletion of the account.
Let S = Let E = Let r = Let s =   

How Much Can You Spend
S = (1 + r)nE/[((1 + r)n - (1 + s)n)/(r - s)]
E is your nest egg, r is the interest rate,
s is the inflation rate, n is the number of years the nest egg must last,
and S is the amount you can afford to spend annually.
Let E = Let r = Let s = Let n =   


Back to Financial Forms Page