How can we help?

Open any formula, fill in every box except the one you want, and tap Solve. DrillSolver works the formula backwards for you. Any box can be the blank one, as long as the formula allows it (a few, like dogleg severity, only solve one or two ways because the maths has more than one answer).

That means the inputs can't happen together. For example, kill mud lighter than the mud in the hole, or a hole smaller than the pipe. The message tells you which number to look at. If you're sure the inputs are right, email us the numbers.

One of the numbers is outside the range you'd normally see for that box, like a fat-fingered 12000 instead of 1200. You still get the answer; it's just a heads-up.

It was saved longer ago than your limit (12 hours unless you change it in Settings → Well Values). Mud weights and depths move, so give it a look before you use it.

Settings → Constants in Formulas. Field uses the numbers on Canadian well control sheets, like 0.00981. Exact uses standard gravity, 0.00980665. Answers can differ in the last digit or two; match whatever your kill sheet uses.

Yes, if your inclination is over 90°. You're drilling up-dip, so the hole is getting shallower.

Settings → Calculator Keys. A key can be a plain number or a bit of maths like 0.0007854/1000. Tap one to edit it, or add your own.

Yes. Type 2 + 2 and press = for 4, then keep pressing = to add 2 each time.

Tap ƒ on the calculator to pick a formula, and your current number is ready to drop into any box. When you've solved, "Use … in Calculator" takes the answer back. Sending numbers both ways is part of Pro.

Pick a method, fill in SIDPP, SICP and pit gain, and it works out kill mud, ICP, FCP, strokes, times, MAASP and a schedule to follow, with a chart. Wait & Weight (vertical or deviated), Driller's, Volumetric, Lubricate & Bleed and Bullheading, plus a ballooning check and LOT/FIT. Depths, pump, SCRs, string and annulus are saved on the well, so on a kick only the kick numbers are new. Part of Pro.

Pick Ballooning Check. With the pumps off, log minutes and the running total back: ballooning tapers off, a kick keeps coming or speeds up. Shut in, and for each small bleed log the time, how much you bled and casing pressure after it settles. Ballooning bleeds off and stays down; pressure that builds back, goes up, or levels off and won't bleed off is an influx. When in doubt, shut in.

MAASP assumes mud from the shoe to surface. Add pit gain, SIDPP and hole TVD and the sheet tracks the gas: once it's above the shoe it has replaced mud there, so casing can go higher by that hydrostatic, up to your surface limit. Until it can track the gas, it holds casing under MAASP the whole way.

For a FIT, enter the EMW to test to and it gives the surface pressure. For a LOT, enter where the line bent over, or log pumped volume and pressure and it picks the bend. Use for the Well saves the leak-off EMW for the kill sheets and the formulas.

Add a well in the Wells tab and tap Use. Every formula you solve while it's active saves its numbers to that well, and they fill in next time. Each well keeps a history of its calcs.

Canadian metric (kPa, kg/m³, m), Metric with bar and SG, and US oilfield (psi, ppg, ft). Pick one in Settings → Units, change single quantities under "Per quantity", or switch any one box with its unit menu.

Free gets the full calculator and five formulas of your choice, with one swap a week. Pro is a one-time purchase that unlocks every formula, the kill sheets, the formula editor, the calculator tape and sending numbers between the calculator and formulas.

Make sure both devices use the same Apple ID, then go to Settings → Your Plan → Restore Purchases.

Apple handles App Store payments, so refunds go through Apple at reportaproblem.apple.com.

No. Everything stays on your devices and in your own iCloud. See the Privacy Policy.