SaaS Revenue Calculator

SaaS revenue compounds because each month's growth applies to a base that already includes last month's growth. This calculator takes a current MRR, applies a constant monthly rate across a projection window, and returns the cumulative revenue billed across that window alongside the MRR the final month reaches.

At 50,000 MRR growing 8% a month, the final month of a 12-month window bills about 116,600, an annual run rate near 1.40 million. Cumulative revenue across the twelve months is about 948,900, well above the 600,000 that flat MRR would produce. The gap between the compounded total and the flat line is what the projection measures.

The model holds one growth rate constant across the whole window. Real books move quarter to quarter with hiring, launches and market conditions, so a projection built on a single rate diverges from one built on a rate that shifts. What the output describes is the shape of constant compounding.

Sample figures

With a current MRR of 50,000, monthly growth of 8% and a 12-month projection, cumulative revenue works out to 948,856.32, the final month bills 116,581.95, and the annual run rate at that point is 1,398,983.40. These are sample figures for illustration rather than a target trajectory.

The levers in this calculation

The three inputs do not carry equal weight, and comparing them fairly needs one basis: a 1% change in each, holding the other two.

Projection Months is the strongest lever whenever the rate is positive, and it holds that place at every positive rate and every window length rather than only at these figures. A 1% longer window lifts the cumulative total by 1.53%.

Current MRR is the only proportional lever, moving the total 1.00% for 1%, exactly. It factors straight out of the series, which is why the two MRR scenarios sit at equal distances either side of the headline.

Monthly Growth is the weakest of the three over a short window and gains on the others as the window lengthens. A 1% change in the rate moves the total by 0.47% at twelve months; it passes the Current MRR lever at a window of twenty-three months, and that crossing arrives later at lower rates: thirty-five months at 5%, fifty-six at 3%, and below about 2.8% it falls outside the sixty-month maximum this calculator accepts. Measured in percentage points instead, the basis a rate is normally discussed in, the same lever looks much larger and is asymmetric: a rise from 8% to 9% adds 6.13% to the total, a fall to 7% removes 5.74%, and the gap between those two widens as the window lengthens, because the rate compounds once for every month in the projection.

The ordering reverses once the book is contracting. Current MRR is exactly proportional whatever the rate does, and neither of the other two levers exceeds one to one at any negative rate, so on a shrinking base the starting figure is what the total is most sensitive to. Which of the other two comes second depends on how deep the contraction runs: at a mild −5% over twelve months the window matters more than the rate, and by −15% that has swapped. At exactly zero the growth lever disappears and the other two are equally proportional, since the total is the starting figure repeated.

Each additional month adds that month's own MRR, the largest figure in the series so far. Stepping from twelve months to thirteen at an 8% rate adds 2.52 times the starting MRR, or 13.3% of the twelve-month total. Each further month adds more in cash than the one before it, though less as a share of a total that is growing alongside it.

How the math works

Cumulative revenue is the geometric series MRR × ((1 + g)^m − 1) ÷ g, where g is the monthly rate as a decimal and m is the number of months. The projection counts the current month as month one and bills it at the MRR entered, applying growth from month two onward, so the final month's MRR is MRR × (1 + g)^(m − 1), which is eleven compounding steps across a twelve-month window, not twelve. Both outputs use that same indexing. At a growth rate of exactly zero the quotient form divides by nothing, so the calculator uses the flat sum instead: MRR multiplied by the month count.