Stihl MS 400 C-M vs. MS 500i (Power Comparison)

The MS 500i makes more rated power: 5.0 kW versus 4.0 kW for the MS 400 C-M, a 25% increase. It also weighs about 0.4 kg more as a powerhead. Choose the 500i for frequent, demanding cuts where that extra output helps; choose the 400 C-M when lower weight matters more than maximum power.

When two professional saws look close on paper, the extra power can seem like an easy win. But the heavier saw is not always the faster choice over a full workday, and a longer bar does not make every cut safer or more suitable. The useful comparison is how each saw’s power and weight fit your wood, cutting time, and skill.

I start with manufacturer specifications, then separate what the numbers show from what they cannot promise. Rated power is a useful comparison, but it does not predict an exact cutting time. Chain condition, bar setup, wood, and operator technique all affect the result.

Power and weight: what the numbers show

The MS 400 C-M is a 66.8 cm³ saw rated at 4.0 kW (5.4 hp), with a listed powerhead weight of 5.8 kg. The MS 500i is a 79.2 cm³ saw rated at 5.0 kW (6.7 hp), with a listed powerhead weight of 6.2 kg. These are powerhead figures, not the weight of a ready-to-cut saw.

The 500i’s power advantage is larger than its powerhead weight increase. A simple power-to-weight calculation gives about 0.69 kW/kg for the 400 C-M and 0.81 kW/kg for the 500i. That is roughly a 17% higher rated power-to-weight figure for the 500i. It is a useful comparison, not a measure of cutting speed or handling comfort.

Powerhead weight does not include the bar, chain, fuel, or oil. The complete saw weighs more, and the bar-and-chain setup changes how it feels in use. As a result, compare complete configurations when possible, not just the figures in a spec table. Key takeaway: The MS 500i offers clearly higher rated output, while the MS 400 C-M saves about 0.4 kg before cutting equipment and fluids are added.

Which saw fits your workload?

Workload fit means matching the saw’s output and complete operating weight to the cuts you do most often. Neither displacement nor a single bar-length rule can settle the choice. Consider wood size, cut frequency, access, operator control, and the bar-and-chain combinations STIHL approves for that exact model and market.

Here are three practical decision cases. They are workload examples, not measured head-to-head test results.

• Frequent large-diameter cuts: If your regular work involves demanding cuts in large wood, the MS 500i’s higher rated power may be useful. It gives you more output on tap, provided the bar, chain, wood, and operator can make good use of it. The saw’s extra weight still matters during repeated handling.
• Mixed cutting with a premium on lower weight: If your work includes varied cuts and you often move or reposition the saw, the MS 400 C-M may be the more suitable balance. It has less rated power, but its lighter powerhead can reduce the weight you handle before the bar and fluids are added.
• Occasional large cuts: Do not choose a 500i on the assumption that more power makes an occasional difficult cut safe. The tree’s condition, cut plan, and operator skill remain decisive. If the work involves a leaning, bound, or tensioned tree, have a qualified faller assess it.

I would first list the cuts you make most often, then identify the largest and most demanding work you expect to do. If the largest cuts are rare, paying and carrying more saw may not serve your everyday work. If demanding cuts are routine, the 500i’s added output may be worth its added weight. Key takeaway: Pick for the work you repeat, not the single biggest cut you can imagine.

Equipment setup, bar and chain compatibility, and safety prep

A compatible setup is one that matches the saw’s approved bar and chain options, including pitch, gauge, and drive-link count. Those details must fit the bar and sprocket. Check the model’s current manual, bar markings, chain markings, and dealer guidance for your market; do not assume a chain that fits one setup fits another.

Choose bar length for the wood and cut, within the combinations STIHL approves for the exact saw. There is no universal displacement-to-bar ratio that makes a setup right for every job. A longer bar can reach farther, but it also changes handling and the demands placed on the saw and operator. Neither model makes oversized or hazardous felling safe.

Before cutting, check the chain brake, throttle lockout, chain catcher, handles, bar, chain tension, and lubrication. Wear a helmet, eye and hearing protection, chainsaw leg protection, gloves, and boots. Clear bystanders and plan an escape route. Assess tree lean, wind, overhead hazards, and hung-up limbs before work begins. Follow ANSI Z133 work practices and applicable OSHA requirements; get qualified help for felling or overhead hazards.

Start the saw on stable ground, following the model’s cold- or warm-start procedure. Keep the chain brake engaged and the chain clear of people and objects. Do not drop-start the saw. Release the brake only when you are holding the saw securely and ready to cut. Key takeaway: Confirm the exact approved setup and complete a safety check before comparing how either saw performs.

Field cutting: match saw power to the cut

Cutting performance is the result of the whole setup and the cut, not engine output alone. A sharp, correctly tensioned chain and a suitable bar matter. So do the wood, stance, and operator control. Extra rated power cannot correct a poor cut plan or make an unsafe tree safe.

Use a secure stance and a two-handed grip, and keep the work within your training. Avoid the upper quadrant at the bar nose, where contact can cause kickback. Do not work within reach of another person. For felling, use a planned notch and controlled hinge only when your training and site conditions support that work.

A particular danger is barber-chairing: a trunk under compression can split upward with great force if the hinge fails or the cut sequence is wrong. Do not improvise cuts on a leaning, bound, or tensioned tree. Set an exclusion zone and have a trained faller assess and control the cut.

In a fair comparison, use the same wood type and similar diameter, with an approved bar-and-chain setup on each saw. Keep chains sharp and tensioned correctly. Note how each handles the work, but do not treat one cut as proof of a universal speed difference. Key takeaway: The 500i has more rated power; actual cutting rate depends on the full setup and the job.

Maintenance, chain sharpening, and manufacturer-specified tuning

Good maintenance keeps both saws working as designed and helps make a power comparison meaningful. Chain sharpening details vary by chain type and manufacturer. Use the sharpening angles and raker-clearance instructions for your specific chain instead of applying one measurement to every chain.

Check chain sharpness and tension, and inspect the bar groove and oil-port area for debris or damage. Use chain oil suited to the conditions and follow STIHL’s instructions for oil choice and flow. Do not rely on a universal oil viscosity or flow-rate figure: conditions and machine settings matter.

Both models use a 50:1 fuel mix with STIHL two-stroke oil or equivalent oil rated for air-cooled two-stroke engines. Follow the manual for fuel handling and service. Idle and wide-open-throttle limits, adjustment steps, and service procedures are model-specific. The MS 400 C-M’s electronic engine management settings should not be altered outside STIHL-authorized service procedures. Key takeaway: Use the manual and correct chain specifications; do not tune either saw by guesswork.

Shutdown, storage, and seasonal fuel care

Safe shutdown is part of the comparison because both saws require the same care at the end of a cut. Engage the chain brake, shut the engine down before setting the saw down or servicing it, and let hot parts cool. Keep refueling away from ignition sources.

After use, clear chips, check the chain for damage and tension, and inspect the bar groove and oil port. Follow the manual for storage and fuel handling, especially if the saw will sit unused. Do not leave mixed-fuel care to guesswork; use STIHL’s directions for the model and fuel product. Key takeaway: A clean inspection after work helps catch setup problems before the next cut.

Bottom line: choose by output need, not badge or displacement

The MS 500i is the power choice: it provides 5.0 kW, 25% more rated output than the MS 400 C-M, for about 7% more powerhead weight. The MS 400 C-M is the lighter option, with 4.0 kW of rated power. Neither figure alone tells you which saw will cut faster in your wood.

If demanding, large cuts are frequent and your setup and skill support the extra output, the 500i is the stronger match. If a lower powerhead weight better suits your usual workload, the 400 C-M deserves serious consideration. Before buying, confirm current local specifications, approved bar and chain combinations, and service support with STIHL or an authorized dealer. The right choice is the one that fits your regular work and lets you maintain control.

Frequently asked questions

These answers summarize the key differences without treating rated power as a promise of cutting speed. Check current STIHL information for your market before purchase, since available configurations and approved bar-and-chain combinations can vary.

Which saw is more powerful?
The MS 500i is rated at 5.0 kW (6.7 hp), compared with 4.0 kW (5.4 hp) for the MS 400 C-M.

How much more power does the MS 500i have?
Its rated power is 25% higher: 5.0 kW compared with 4.0 kW.

How much heavier is the MS 500i?
Its listed powerhead weight is 0.4 kg higher: 6.2 kg versus 5.8 kg. Bar, chain, fuel, and oil add weight to both.

Does the MS 500i always cut faster?
No. Rated power is only one factor. Chain sharpness, bar setup, wood, and operator technique affect cutting rate.

Which saw is better for frequent demanding cuts?
The MS 500i has more rated output and may suit frequent demanding cuts when the operator and approved setup can use it safely.

Which is the lighter option?
The MS 400 C-M, at a listed powerhead weight of 5.8 kg. Compare complete saw weights for the setup you plan to use.

Can I choose a bar by engine size alone?
No. Use only combinations approved for the specific model and market, and match chain pitch, gauge, and drive-link count to the bar and sprocket.

Do both saws use a 50:1 fuel mix?
Both use a 50:1 mix with STIHL two-stroke oil or equivalent oil rated for air-cooled two-stroke engines. Follow the current manual for details.

(This article was written by one of our staff writers, Marcus Thorne. Visit our Meet the Team page.)