Most companies treat forecasting like a one-time effort. Build it once, check a box, and move on. But revenue forecasting isn’t just about projecting growth. It’s about building a system that helps you see what’s coming, and react while there’s still time.
It’s how you avoid hiring too early. Or fundraising too late. It’s how you steer the business with your eyes open.
In this guide, we’ll build a SaaS revenue forecast from scratch. You’ll see how to structure drivers, layer in costs and seasonality, map sales quotas, and keep it all live. Every number will flow into the next… the way it actually should.
Why revenue forecasting matters
Good forecasts show you the future before it even happens. They tell you when churn might spike, when you’ll need to hire, when cash could get tight, and if your targets are even realistic.
But it’s not just about foresight. It’s about coordination.
When the revenue forecast is solid, sales knows what to aim for. Finance knows what it’ll cost. And leadership has a real sense of whether growth is sustainable, or just wishful thinking.
Without forecasting, you don’t get that. You get guesses. You get chaos. You get teams rowing in different directions.
And it shows up later, when you’re already behind.
What to gather before you start
Great revenue forecasting starts with good inputs. Here’s what you’ll need:
- Customer and revenue data: At least 12 months of MRR, churn, expansion, and pricing.
- Sales assumptions: Pipeline velocity, win rates, new customers by tier.
- Cost structure: Salaries, variable costs, CAC, commissions.
- Seasonality: Month-by-month shifts in signups or close rates.
- Sales team plan: Quotas, start dates, roles, ramp.
You’ll feed all of this into Runway. Once it’s in, everything connects—from bookings to costs to runway.
Building a live SaaS revenue forecast in Runway
Let’s say you’re building a forecast for a company called DataFlow.
You sell three pricing tiers:
- Starter – $99/mo
- Professional – $499/mo
- Enterprise – $2,499/mo
Your current customers look like this:
- 150 on Starter
- 40 on Professional
- 8 on Enterprise
You plug that into Runway’s customer database. Then you set churn and upgrade assumptions:
- Starter churn: 5% monthly
- Pro churn: 3%
- Enterprise churn: 2%
- Upgrades: 10% move from Starter to Pro yearly, 5% from Pro to Enterprise
Next, you model acquisition:
- Self-serve: +25 Starter per month
- Sales-led: +8 Pro and +2 Enterprise per month
Just build your formulas, and Runway will turn all that into MRR and ARR by tier—live. Change churn or bookings and your entire revenue forecasting model updates instantly.
Mapping cost drivers and expenses
Costs in SaaS aren’t flat. Some grow with customers, some grow with revenue, some grow with headcount.
Here’s what DataFlow models:
- Fixed monthly costs:
Salaries – $85,000
Office/tools – $8,000 - Variable costs:
Hosting – $8 per customer
Payments – 2.9% of revenue
Success – $200 per Enterprise customer - Growth investments:
Marketing – $15,000
Commissions – 10% of new bookings
Headcount plans go in too:
- Hire 2 AEs in Q2 at $70K/year
- Ramp: 2 months training → full quota in 6
- Runway ties their salaries and commissions to hiring dates
The result: as reps ramp up, your expenses and revenue forecast adjust automatically.
Applying seasonality to your forecast
Seasonality can skew your numbers if you don’t factor it in.
DataFlow sees:
- Enterprise deals spike in Q4
- Pro slows in summer
- Starter dips in December
Runway models this using monthly multipliers:
- Enterprise: 150% in Q4
- Pro: 70% in July/Aug
- Starter: 60% in Dec
Add these to your acquisition and upgrade drivers. Use date formulas so they repeat yearly. Want to segment by industry? Add overrides. The patterns stay realistic, not generic.
Modeling sales quotas and ramp
Revenue doesn’t just appear. It comes from rep capacity.
In Runway, you add a sales team database:
- Name, role, start date, quota
- Ramp:
Months 1–2 → 0%
Months 3–4 → 50%
Months 5–6 → 75%
Month 7+ → 100% - Attainment: 85% average
Now you calculate bookings capacity:
- Monthly quota × attainment × ramp schedule
- Split capacity by tier
Add those Q2 hires. Their quotas get rolled into bookings, revenue, and ultimately cash. No manual updates required.
For more, see how to plan revenue with a strong sales capacity model.
What a connected revenue forecast unlocks
Once built, this forecast gives you a live view of your business:
- MRR/ARR by tier, with churn and upgrades applied
- Bookings from quotas, converted into new customers
- Gross margin, layered with cost drivers
- OpEx from headcount, including ramp and commissions
- Runway, updated with every change
You can tweak any variable—churn, hiring, pricing—and see everything ripple across the model. This is real-time revenue forecasting. Not static. Never stale.
Forecasting that stays current
The problem with spreadsheets is that they don’t update themselves. But Runway does.
Every time you sync actuals—revenue, churn, headcount—the forecast updates. Missed quota? It shows. Extra hires? They show too.
And because it’s structured, you can test scenarios fast:
- What if churn ticks up 1%?
- What if Q2 hires shift to Q3?
- What if quota jumps?
Use Runway’s scenario planning to test, compare, and adjust without rebuilding anything.
Why revenue forecasting is easier in Runway
Forecasting in spreadsheets means wrestling with linked tabs and broken formulas.
In Runway, it’s built in.
- Drivers are structured and visible
- Date math is automatic
- Seasonality and ramp work out of the box
- Actuals stay in sync
You can build a revenue forecasting model in days (not weeks). And when the business changes, your plan doesn’t break.
Ready to get started?
Revenue forecasting shouldn’t be a burden. It should be the thing that gives you clarity, aligns your teams, and help you grow without flying blind.
Try Runway and see how fast you can go from scattered data to shared understanding.