How to Compare This Month vs Last Month in Excel

"How did we do compared to last month?"

It's the most common business question. And yet, many people struggle to answer it clearly with their data.

Here's how to do it properly in Excel.

The Basic Comparison

Let's say you have:

• This month's revenue: $52,000
• Last month's revenue: $48,000

Calculate the Difference

=This_Month - Last_Month
=$52,000 - $48,000
=$4,000

Simple. You made $4,000 more this month.

Calculate the Percentage Change

The difference alone doesn't tell the full story. Is $4,000 a lot? Depends on the base.

=(This_Month - Last_Month) / Last_Month
=($52,000 - $48,000) / $48,000
=8.33%

You grew 8.33%. That's meaningful context.

Format as percentage: Select the cell → Format → Percentage

Setting Up a Monthly Comparison Table

Here's a practical setup:

| Month | Revenue | vs Last Month | % Change | |-------|---------|---------------|----------| | Jan | $45,000 | - | - | | Feb | $48,000 | $3,000 | 6.67% | | Mar | $52,000 | $4,000 | 8.33% | | Apr | $49,000 | -$3,000 | -5.77% |

Formulas

Column C (vs Last Month):

=B3-B2

Column D (% Change):

=(B3-B2)/B2

Drag both formulas down for all months.

Comparing Multiple Metrics

Usually you want to compare more than just revenue:

| Metric | This Month | Last Month | Change | % Change | |--------|------------|------------|--------|----------| | Revenue | $52,000 | $48,000 | $4,000 | 8.33% | | Orders | 520 | 480 | 40 | 8.33% | | Avg Order | $100 | $100 | $0 | 0% | | New Customers | 85 | 92 | -7 | -7.61% |

This view immediately shows: revenue is up because orders are up, but new customer acquisition is actually declining. That's an insight.

Conditional Formatting for Quick Reading

Make positive changes green, negative changes red:

1. Select your % Change column
2. Home → Conditional Formatting → Color Scales
3. Or use Icon Sets (arrows up/down)

Custom rule for positive/negative:

1. Conditional Formatting → New Rule
2. "Format cells that contain"
3. Cell Value > 0 → Green fill
4. Cell Value < 0 → Red fill

Handling Edge Cases

What if Last Month is Zero?

Dividing by zero gives an error. Handle it:

=IF(B2=0, "N/A", (B3-B2)/B2)

Or show infinite growth:

=IF(B2=0, "New", (B3-B2)/B2)

What About Negative Numbers?

If you're comparing profits that can be negative:

=IF(B2=0, "N/A", IF(AND(B2<0, B3>0), "Turned Positive", (B3-B2)/ABS(B2)))

This handles the case where you went from -$10K to +$5K.

Comparing Same Month Last Year

Month-over-month can be misleading due to seasonality. Compare to the same month last year:

=This_Month - Same_Month_Last_Year

Example:

• December 2025: $85,000
• November 2025: $52,000 (MoM: +63%)
• December 2024: $78,000 (YoY: +9%)

The MoM growth looks amazing, but it's mostly seasonal. YoY shows the real growth: 9%.

Creating a Simple Dashboard

Combine everything into a quick view:

Key Metrics Box

┌─────────────────────────────────────┐
│  DECEMBER 2025 vs NOVEMBER 2025    │
├─────────────────────────────────────┤
│  Revenue:    $52,000  ▲ 8.3%       │
│  Orders:     520      ▲ 8.3%       │
│  Customers:  85       ▼ 7.6%       │
│  Avg Order:  $100     → 0%         │
└─────────────────────────────────────┘

Mini Sparklines

Add sparklines to show the trend:

1. Select cell for sparkline
2. Insert → Sparklines → Line
3. Select last 6-12 months of data

Now you see not just the comparison, but the trend.

Common Mistakes

Mistake 1: Comparing Unequal Periods

Comparing a 31-day month to a 28-day month? That's not fair. Consider:

• Revenue per day
• Normalized to 30 days
• Or just note the caveat

Mistake 2: Ignoring Outliers

One huge order can skew a month. Look at median values or exclude anomalies for a clearer picture.

Mistake 3: Only Looking at One Metric

Revenue up 20% sounds great until you realize costs went up 30%. Always compare multiple related metrics.

Automating Monthly Comparisons

If you do this every month:

Option 1: Template

Create a template where you just paste new data. Formulas update automatically.

Option 2: Pivot Tables

Set up a pivot table that automatically calculates period comparisons when you refresh data.

Option 3: AI Tools

Upload your data and get automatic period comparisons with insights about what changed and why.

Quick Reference

| Want to Calculate | Formula | |-------------------|---------| | Difference | =New - Old | | % Change | =(New - Old) / Old | | Growth Rate | =(New / Old) - 1 | | % of Previous | =New / Old |

Start Comparing

Open your latest monthly data. Calculate the % change for your top 3-5 metrics. Look for:

1. What improved?
2. What declined?
3. Are the changes connected?

That's your monthly business health check in 5 minutes.

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Related Articles

• How to Track Business Growth Month Over Month
• What Business Metrics Should You Track Monthly
• How to Create a Weekly Business Report in 5 Minutes

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