ksp orbit calculator

Plan circular orbit speed, orbital period, and Hohmann transfer delta-v between two circular orbits around a selected body.

Celestial Body

Gravitational Parameter μ (m³/s²)

Body Radius (m)

Initial Orbit Altitude (km)

Target Orbit Altitude (km)

Optional Plane Change (degrees)

Assumptions: two-body physics, instantaneous burns, no atmosphere, no drag, and no gravity losses.

Why use a KSP orbit calculator?

Kerbal Space Program rewards intuition, experimentation, and a little math. This calculator is for the moments when you want fast, practical numbers before placing maneuver nodes. Instead of guessing how much fuel a transfer needs, you can estimate the burn plan in seconds and build rockets with tighter margins.

The tool focuses on one of the most common mission tasks: transferring between two circular orbits around the same body. That means it is perfect for low orbit adjustments, station rendezvous prep, and early mission design.

What this calculator gives you

1) Circular orbit stats

Initial circular orbit velocity
Target circular orbit velocity
Initial and target orbital periods

2) Hohmann transfer burn plan

First burn (at initial orbit): transfer injection
Second burn (at target altitude): circularization
Total transfer delta-v
Coast time from burn 1 to burn 2 (half transfer orbit)

3) Optional plane change estimate

If you include an inclination difference, the calculator estimates the pure plane-change cost at initial orbit speed. This is useful for rough budgeting, especially if you are deciding whether to launch into a matching plane or fix it later.

The equations behind the numbers

Everything here uses standard orbital mechanics with KSP body constants. Inputs are converted to meters and seconds internally.

r = R + h
v_circ = √(μ / r)
T = 2π √(r³ / μ)

a_t = (r₁ + r₂) / 2
v_t1 = √(μ(2/r₁ - 1/a_t))
v_t2 = √(μ(2/r₂ - 1/a_t))
Δv₁ = |v_t1 - v₁|
Δv₂ = |v₂ - v_t2|
t_transfer = π √(a_t³ / μ)

Δv_plane = 2v sin(Δi/2)

How to use this during gameplay

Select your current SOI body (Kerbin, Mun, Minmus, etc.).
Enter initial and target altitudes in kilometers.
Press Calculate Orbit Plan.
Create maneuver node burn 1 near periapsis for orbit raising (or apoapsis for lowering).
Coast to the opposite side of the transfer ellipse and execute burn 2 to circularize.
Add 5-15% delta-v margin for piloting and finite burn effects.

Example mission thinking

Kerbin 80 km → 120 km parking orbit raise

This is a small transfer and a great sanity check for your reaction wheel, TWR, and RCS setup. You should see a modest two-burn plan, usually on the order of only a few dozen m/s per burn. If your craft needs far more than expected, check staging, dry mass, and whether you accidentally included atmospheric drag conditions in your mental model.

Low Mun orbit adjustments

Around lower-gravity bodies like the Mun or Minmus, burn costs are much smaller, but timing and precision become more important. Small overburns produce larger orbital shape errors, so this calculator helps you set a realistic burn magnitude before fine-tuning.

Common mistakes that waste fuel

Trying to change inclination in low, high-speed orbit when it can be done cheaper at apoapsis.
Circularizing at the wrong point of the transfer ellipse.
Ignoring unit consistency (km in the UI, meters in equations).
Planning with no reserve for steering losses and imperfect execution.
Forgetting that atmospheric bodies (Kerbin, Eve, Duna) can invalidate vacuum-only assumptions at low altitudes.

Limitations and scope

This page is intentionally focused and fast. It does not calculate interplanetary transfer windows, patched-conic ejection burns, aerobraking, low-thrust trajectories, or n-body perturbations. For those, pair this tool with in-game maneuver nodes, Transfer Window Planner mods, or more advanced mission software.

For everyday KSP play, though, this calculator covers a huge chunk of orbital housekeeping and gives you dependable first-pass numbers.