What Is Burn Rate?

Burn rate is the speed at which a project consumes its allocated budget. In professional services, it's the rate at which labour hours and the costs those hours represent are being spent relative to what was planned at project outset.

A project with a £50,000 budget that has consumed £30,000 in the first half of its timeline will have a burn rate leading to a £60,000 final cost, a 20% overrun, unless the delivery pace changes. Burn rate shows if that trajectory is acceptable before the budget runs out.

How Burn Rate Works

Burn rate is calculated and monitored in two ways in PS project management:

1. Cost-based burn rate is budget consumed divided by time elapsed. If a project spends £20,000 of its £60,000 budget in the first two weeks of a six-week project, it burns £10,000 per week, matching the planned rate and is on track. If it spends £25,000 in two weeks, it burns £12,500 per week, 25% over the planned rate​

2. Hours-based burn rate is hours consumed divided by total budgeted hours. This is often more actionable for PS firms because it removes rate variations and focuses on delivery effort. A project budgeted at 200 hours with 80 hours consumed after one-third of the timeline runs slightly hot.

The critical comparison is burn rate against completion percentage. A project that has consumed 60% of its budget but is only 40% complete has a problem. A project that has consumed 60% of its budget and is 65% complete is slightly ahead.

Earned Value Management (EVM) formalizes this comparison - it calls the comparison of budget consumed to work completed the Cost Performance Index (CPI). CPI below 1.0 means you're spending more than the work is worth; above 1.0 means you're under-delivering on spend (which occasionally signals a scope problem in the other direction).

Why Burn Rate Matters for Professional Services

In professional services firms, the margin on any project is largely set at estimation. Once underway, every hour of overrun on a fixed-fee contract directly reduces gross margin. Burn rate monitoring provides a window to intervene before the budget is spent.

The two most common failure modes are:

Front-loaded burn occurs when senior staff do more work than is scoped during the discovery and setup phases. The project appears to be on track with the timeline, but has already used a disproportionate share of the budget before most deliveries begin.​

Gradual drift happens when small daily overruns accumulate unnoticed. Each week is slightly over plan. By week six of an eight-week project, 85% of the budget is spent while only 65% of the work is done.

Both failure modes are preventable with weekly burn rate monitoring. Neither appears in a monthly financial review until it is too late to recover margin.

Magnetic's project management module tracks burn rate in real time, showing budget consumed, hours tracked, and projected final cost as timesheets are submitted instead of waiting until month end.

Burn Rate vs Budget Variance

These are related but answer different questions:

‍

Burn rate is predictive; budget variance is descriptive. You need both. Budget variance shows where you are; burn rate shows where you are going.

Examples in Practice

Example 1 - Early warning caught in time A consultancy runs a 10-week fixed-fee strategy engagement budgeted at £40,000. After week 3, burn rate tracking shows £16,000 consumed, 40% of the budget for 30% of the timeline. The project manager alerts the account director. On review, the discovery phase used more senior time than estimated. The remaining scope is rebalanced: two planned senior workshop sessions are restructured to include junior analysts, bringing the projected final cost back to £42,000. Margin is preserved within an acceptable range.

Example 2 - Burn rate ignored until too late An agency runs a fixed-price website build with no burn rate tracking. At the final review, time tracking shows 340 hours logged against a 240-hour budget. At a blended rate of £85/hour, the overage is £8,500, wiping out the project's margin and causing a net loss. The finance manager sees this only after invoicing is complete and the retrospective is closed.

Example 3 - Retainer burn rate management A PR agency manages 12 monthly retainers, each with a fixed fee covering a set number of hours. Midmonth burn rate tracking reveals two clients consuming hours at 1.5 times the planned rate, both on track to exceed their retainer hours by week 3. Account managers contact both clients to discuss scope. One agrees to a top-up fee; the other defers requests to the next month. Overservicing is contained.

Common Mistakes

Checking burn rate only at month-end is too late, as the budget is already spent. Burn rate monitoring aims to detect trajectory problems before it is too late to change course. This means checking active projects at least weekly.

Using invoiced amounts instead of cost is incorrect. Burn rate should be calculated on cost (hours times labour rate), not on revenue invoiced or percentage billed. The timing of invoicing can mask the actual pace of delivery effort.

Treating all burn equally is misleading. High burn early in a project (discovery, setup) is often normal. High burn late in a project (delivery, QA) may signal scope expansion or underestimation of remaining work. Context matters. Burn rate should be read against the project phase.

Not separating client-requested changes from original scope causes confusion. If a client adds work mid-project, burn rate will increase, but this differs from overspend against the original scope. Track change orders separately so burn rate reflects delivery performance rather than scope growth.

‍