Excel Financial Modelling: A Beginner's Guide

What financial modelling actually means

A financial model is a spreadsheet that represents a business or investment numerically — projecting revenue, costs, profit, cash flow, and key metrics. The goal is to make assumptions explicit and show how they flow through to outcomes. Change one assumption and the whole model updates.

The three-section structure

Inputs/Assumptions — all your variable inputs in one place, clearly labelled, with units
Calculations — formulas that reference the inputs, never hardcoded numbers
Outputs — summary metrics, charts, the numbers decision-makers actually use

The golden rule — no hardcoded numbers in formulas

WRONG:  =B5 * 0.08
RIGHT:  =B5 * TaxRate    (where TaxRate is a named cell in your inputs)

Every number that could change should be in an input cell, not buried inside a formula. This is the single most important modelling discipline.

Essential financial modelling formulas

Revenue growth:   =prior_year * (1 + growth_rate)
Gross profit:     =Revenue - COGS
EBITDA margin:    =EBITDA / Revenue
NPV:              =NPV(discount_rate, cash_flows) + initial_investment
IRR:              =IRR(all_cash_flows_including_initial)
Debt service:     =PMT(interest_rate/12, term_months, -loan_amount)

Model integrity checks

Always build a check row or sheet that flags if the model is broken:

=IF(ABS(Assets - Liabilities - Equity) < 0.01, "OK", "ERROR")
-- Balance sheet check: assets must equal liabilities + equity
=IF(SUM(revenue_by_segment) = total_revenue, "OK", "ERROR")
-- Totals check: segments must add up to total

💡 Colour code your model

Standard convention: blue text for hardcoded inputs, black for formulas, green for outputs/checks. Anyone picking up your model immediately knows which cells to change and which to leave alone.

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Excel financial modellinga beginner's guide