Bookkeeping Calculator

Bookkeeping Formulas Cheat Sheet

Every formula used by the calculators on one page, each with a worked example. Handy for revision and for FNSACC323 Perform financial calculations.

Bookkeeping Formula Reference

Every formula used by these calculators. They match the FNSACC323 Perform financial calculations unit.

Tax
GST: Add
Price inc GST = Price ex GST × 1.1
e.g. $100 × 1.1 = $110
GST: Remove
Price ex GST = Price inc GST ÷ 1.1
e.g. $110 ÷ 1.1 = $100
GST: Find Amount
GST = Price inc GST ÷ 11
e.g. $110 ÷ 11 = $10
Business
Markup
Selling Price = Cost + (Markup% × Cost)
e.g. Cost $50, Markup 20% → SP = $50 + ($50 × 0.20) = $60
Profit Margin
Selling Price = Cost ÷ (1 − Margin%)
e.g. Cost $50, Margin 20% → SP = $50 ÷ 0.80 = $62.50
Sales Commission
Commission = Rate% × Total Sales
e.g. $10,000 sales at 5% → Commission = $500
Simple Interest
Simple Interest
Interest = Principal × Rate × Number of Periods (T)
I = P × R × T
e.g. $300 at 2% for 1 year → I = $300 × 0.02 × 1 = $6
Total Value / Total Repayable
Total = Principal + Interest
e.g. $300 + $6 = $306
Compound Interest
Future Value (Compound)
FV = PV × (1 + i/n)^(n×t)
PV = present value, i = annual rate, n = periods/year, t = years
Present Value
PV = FV × (1 + i/n)^(−n×t)
How much to invest now to reach a future target
Loan Repayment
Repayment = P × [rp × (1 + rp)^N] ÷ [(1 + rp)^N − 1]
rp = rate per period, N = total periods
Depreciation
Straight Line: No Residual
Depreciation = Total Cost ÷ Effective Life
e.g. $11,000 ÷ 5 yrs = $2,200 per year (same each year)
Straight Line: With Residual
Depreciation = (Total Cost − Residual) ÷ Effective Life
e.g. ($11,000 − $1,000) ÷ 5 = $2,000 per year
Diminishing Value: Rate
Rate % = 200% ÷ Effective Life
e.g. 200 ÷ 12 yrs = 16.67%
Diminishing Value: Depreciation
Depreciation = Rate % × Carrying Amount
Applied to the reducing book value each year, bigger early, smaller later

GST Calculator (Australia)

GST Rate: 10%
$

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Markup / Profit Margin

Markup calculates profit as a percentage of the cost price. Profit Margin calculates profit as a percentage of the selling price.

SP = Cost + (Markup% × Cost)
$
%

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Sales Commission

Commission = Rate% × Total Sales
$
%
$

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Break-Even Point

Units = Fixed Costs ÷ (Price − Variable Cost)

Fixed Costs stay the same no matter how much you sell (e.g. rent, insurance). Variable Cost is what it costs to make or deliver one single unit (materials, packaging, per-item shipping) — it goes up and down with sales, unlike fixed costs. Selling Price is what you charge per unit.

$
$
$

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Simple Interest

I = P × R × T
$
%

Results

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Compound Interest

FV = PV × (1 + I)ᴺ
$
%
$

Results

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Present Value

PV = FV × (1 + I)⁻ᴺ
$
%

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Depreciation

Depn = (Cost − Residual) ÷ Life
$
$

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Time to Decimal

Decimal Hours = Hours + (Minutes ÷ 60)
hrs
min

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Pay Calculator (Before Tax)

Gross Pay = (Rate × Ord. Hours) + (Rate × OT × OT Hours)
$

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GST / VAT / Sales Tax Calculator

Rate: 15%
%
$

Results

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How to use this page

The reference above groups the formulas by topic: tax, business, simple interest, compound interest and depreciation. Each one links to a calculator that applies it and shows the working step by step.

Tips for assessments

Write the formula first, substitute the numbers on the next line, then give the answer with its unit ($, %, units or years). Convert percentages to decimals before multiplying (5% becomes 0.05), and round money to two decimal places only at the final step.

Frequently asked questions

What formulas do I need for FNSACC323?

The unit covers everyday financial calculations: GST, markup and margin, commission, simple and compound interest, and depreciation. All of them are listed on this page.

How do I turn a percentage into a decimal?

Divide by 100. 12.5% becomes 0.125.

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